Piezoelectric/electrostrictive device and method of manufacturing same

ABSTRACT

A piezoelectric/electrostrictive (P/E) device includes at least one actuator section secured to thin plate sections with an adhesive. The actuator section includes a multilayered member including at least three actuator films, each of which include a P/E layer and electrode films. One or more holes or recesses are formed in portions of the thin plate sections on which the P/E elements are formed. The electrode films contact upper and lower surfaces of respective P/E layers and alternately extend to opposite surfaces thereof. End surface electrodes electrically connect an electrode film that contacts one of the P/E layers and an electrode film that contacts another one of the P/E layers. The end surface electrodes are electrically connected to terminals which are provided on a surface of an outermost layer of the P/E layers, and which are separated from one another by a predetermined distance.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 09/672,069filed Sep. 28, 2000, which in turn is a continuation-in-part of U.S.application Ser. No. 09/524,042 filed Mar. 13, 2000 now U.S. Pat. No.6,498,419, and which claim the benefit of U.S. Provisional ApplicationSer. No. 60/204,702 filed May 16, 2000, the entireties of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a piezoelectric/electrostrictive devicewhich is provided with a movable section to be operated on the basis ofa displacement action of a piezoelectric/electrostrictive element, or apiezoelectric/electrostrictive device which is capable of detectingdisplacement of a movable section by the aid of apiezoelectric/electrostrictive element, and a method for producing thesame. In particular, the present invention relates to apiezoelectric/electrostrictive device which is excellent in strength,shock resistance, and moisture resistance and which makes it possible toefficiently operate a movable section to a great extent, and a methodfor producing the same.

2. Description of the Related Art

Recently, a displacement element, which makes it possible to adjust theoptical path length and the position in an order of submicron, isrequired, for example, in the fields of optical science, magneticrecording, and precision machining. Development is advanced for thedisplacement element based on the use of the displacement brought aboutby the inverse piezoelectric effect or the electrostrictive effectcaused when a voltage is applied to a piezoelectric/electrostrictivematerial (for example, a ferroelectric material).

As shown in FIG. 53, for example, those hitherto disclosed as such adisplacement element include a piezoelectric actuator comprising afixation section 404, a movable section 406, and a beam section 408 forsupporting them which are formed in an integrated manner with a hole 402provided through a plate-shaped member 400 composed of apiezoelectric/electrostrictive material and with an electrode layer 410provided on the beam section 408 (see, for example, Japanese Laid-OpenPatent Publication No. 10-136665).

The piezoelectric actuator is operated such that when a voltage isapplied to the electrode layer 410, the beam section 408 makes extensionand contraction in a direction along a line obtained by connecting thefixation section 404 and the movable section 406 in accordance with theinverse piezoelectric effect or the electrostrictive effect. Therefore,the movable section 406 can perform circular arc-shaped displacement orrotational displacement in the plane of the plate-shaped member 400.

On the other hand, Japanese Laid-Open Patent Publication No. 63-64640discloses a technique in relation to an actuator based on the use of abimorph. In this technique, electrodes for the bimorph are provided in adivided manner. The divided electrodes are selectively driven, and thusthe highly accurate positioning is performed at a high speed. Thispatent document (especially in FIG. 4) discloses a structure in which,for example, two bimorphs are used in an opposed manner.

However, the piezoelectric actuator described above involves such aproblem that the amount of operation of the movable section 406 issmall, because the displacement in the direction of extension andcontraction of the piezoelectric/electrostrictive material (i.e., in thein-plane direction of the plate-shaped member 400) is transmitted to themovable section 406 as it is.

All of the parts of the piezoelectric actuator are made of thepiezoelectric/electrostrictive material which is a fragile materialhaving a relatively heavy weight. Therefore, the following problemsarise. That is, the mechanical strength is low, and the piezoelectricactuator is inferior in handling performance, shock resistance, andmoisture resistance. Further, the piezoelectric actuator itself isheavy, and its operation tends to be affected by harmful vibrations (forexample, residual vibration and noise vibration during high speedoperation).

In order to solve the problems described above, it has been suggestedthat the hole 402 is filled with a filler material having flexibility.However, it is clear that the amount of displacement, which is broughtabout by the inverse piezoelectric effect or the electrostrictiveeffect, is decreased even when the filler material is merely used.

SUMMARY OF THE INVENTION

The present invention has been made taking the foregoing problems intoconsideration, an object of which is to provide apiezoelectric/electrostrictive device and a method for producing thesame which make it possible to obtain a displacement element that isscarcely affected by harmful vibration and capable of high speedresponse with high mechanical strength while being excellent in handlingperformance, shock resistance, and moisture resistance, making itpossible to realize a long life time of a device, and improve thehandling performance of the device and the attachment performance forparts to be attached to the movable section or the fixation performanceof the device, so that the movable section may be greatly displaced at arelatively low voltage, and it is possible to achieve a high speed ofthe displacement action of the device, especially of the movable section(realization of a high resonance frequency), as well as a sensor elementwhich makes it possible to accurately detect vibration of the movablesection.

According to the present invention, there is provided apiezoelectric/electrostrictive device comprising at least an actuatorsection including a stacked type piezoelectric/electrostrictive elementsecured onto a thin plate section made of metal with an adhesiveintervening therebetween; wherein an actuator film of the stacked typepiezoelectric/electrostrictive element, which is composed ofpiezoelectric/electrostrictive layers and electrode films, isconstructed by a multilayered member including at least three layers ormore.

Accordingly, the thin plate section can be displaced to a great extenteven when the areal size of the stacked typepiezoelectric/electrostrictive element is not widened on the plane.Further, the piezoelectric/electrostrictive device is excellent instrength and toughness, because the thin plate section is made of metal.Further, it is possible to correspond to the quick displacement action.

In other words, according to the present invention, it is possible tosufficiently respond to any variation of the environment of use and anysevere state of use. The piezoelectric/electrostrictive device isexcellent in shock resistance, and it is possible to realize a long lifetime of the piezoelectric/electrostrictive device and improve thehandling performance of the piezoelectric/electrostrictive device.Further, the thin plate section can be greatly displaced at a relativelylow voltage. The rigidity of the thin plate section is high, the filmthickness of the actuator film is thick, and the rigidity thereof ishigh. Therefore, it is possible to achieve a high speed of thedisplacement action of the thin plate section (realize a high resonancefrequency).

It is preferable that the plurality of electrode films, which areincluded in the multilayered member for constructing thepiezoelectric/electrostrictive element, are stacked to have alternateend surfaces, and they are connected so that an identical voltage isapplied to every other layer. It is preferable that the actuator film iscomposed of the multilayered member having ten layers or less. It ispreferable that the actuator film is formed by means of a multilayerprinting method. Further, it is preferable that a positional discrepancyin an in-plane direction, which possibly occurs on a perpendicularprojection plane of each of the electrode films disposed as every otherlayer, is not more than 50 μm. It is preferable that the adhesive has athickness of not more than 15 μm.

In the present invention, it is also preferable that an underlying layeris formed on a surface of the piezoelectric/electrostrictive elementopposed to the thin plate section. It is also preferable that one ormore holes or recesses are formed at least at a portion of the thinplate section at which the piezoelectric/electrostrictive element isformed. In this arrangement, the adhesive enters the interior of thehole or the recess, and hence the adhesion area is substantiallyincreased. Further, it is possible to achieve a thinner adhesive layer.It is also preferable that at least a portion of a surface of the thinplate section, on which the piezoelectric/electrostrictive element isformed, is a rough surface. In this arrangement, the adhesion area issubstantially increased, and hence the adhesion can be tightly effected.

According to another aspect of the present invention, there is provideda piezoelectric/electrostrictive device comprising a pair of mutuallyopposing thin plate sections made of metal and a fixation section forsupporting the thin plate sections, and including an actuator sectionwith a stacked type piezoelectric/electrostrictive element fixed on atleast one of the thin plate sections by the aid of an adhesive; whereinthe stacked type piezoelectric/electrostrictive element is composed of aplurality of piezoelectric/electrostrictive layers and electrode films;and the electrode films, which contact with upper and lower surfaces ofthe respective piezoelectric/electrostrictive layers, are alternatelyled to opposite end surfaces, and end surface electrodes, whichelectrically connect the respective electrode films alternately led tothe opposite end surfaces, are electrically connected to terminals whichare provided on a surface of an outermost layer of thepiezoelectric/electrostrictive layer and which are arranged while beingseparated from each other by a predetermined distance respectively.Accordingly, the driving signal can be easily supplied, and thedetection signal can be easily obtained with respect to the stackedpiezoelectric/electrostrictive element. It is possible to realize theformation of the stacked type piezoelectric/electrostrictive element onthe thin plate section.

In the invention described above, it is also preferable that the stackedtype piezoelectric/electrostrictive element has a substantiallyrectangular parallelepiped-shaped configuration. It is preferable thatthe predetermined distance between the terminals is not less than 50 μm.It is also preferable that at least one of the terminals and one of theend surface electrodes are electrically connected with each other withan electrode film having a film thickness which is thinner than those ofthe terminal and the end surface electrode.

According to still another aspect of the present invention, there isprovided a piezoelectric/electrostrictive device includes a pair ofmutually opposing thin plate sections, and a fixation section forsupporting the thin plate sections; and one or morepiezoelectric/electrostrictive elements arranged on at least one thinplate section of the pair of thin plate sections; wherein a minimumresonance frequency of the device structure, which is obtained when anobject member having a size substantially equivalent to that of thefixation section exists between open ends of the pair of thin platesections, is not less than 20 kHz, and a relative displacement amountbetween the object member and the fixation section is not less than 0.5μm at a substantial applied voltage of 30 V at a frequency which is notmore than ¼ of the resonance frequency.

Accordingly, it is possible to greatly displace the pair of thin platesections. Further, it is possible to achieve realization of a high speed(realization of a high resonance frequency) for the displacement actionof the device, especially of the pair of thin plate sections.Furthermore, it is possible to obtain a displacement element which isscarcely affected by harmful vibration, which is capable of performinghigh speed response, which has high mechanical strength, and which isexcellent is handling performance, shock resistance, and moistureresistance. Moreover, it is possible to obtain a sensor element whichmakes it possible to accurately detect the vibration of the movablesection.

At least the thin plate section and the fixation section may beconstructed by using ceramics or metal. The respective components may beconstructed with ceramic materials, or they may be constructed withmetal materials. Further, the respective components may be constructedas a hybrid structure obtained by combining those produced from ceramicand metal materials.

It is preferable that when an adhesive intervenes between thepiezoelectric/electrostrictive element and the thin plate section, theadhesive has a thickness which is not more than 10% of a thickness ofthe piezoelectric/electrostrictive element. It is preferable that whenone or more piezoelectric/electrostrictive elements are arranged on onethin plate section of the pair of thin plate sections, a thickness ofthe one thin plate section is thicker than a thickness of the other thinplate section.

It is preferable that when the object member intervenes between the openends of the pair of thin plate sections, then a distance concerning thepair of thin plate sections between a boundary portion with respect tothe object member and a boundary portion with respect to the fixationsection is not less than 0.4 mm and not more than 2 mm, and each of thepair of thin plate sections has a thickness which is not less than 10 μmand not more than 100 μm.

It is preferable that the piezoelectric/electrostrictive element isconstructed by multilayered member including at least three or moreactuator films, which is composed of piezoelectric/electrostrictivelayers and electrode films. In this arrangement, it is preferable thatthe actuator film is composed of the multilayered member having tenlayers or less. Further, it is preferable that thepiezoelectric/electrostrictive layer has a thickness which is not lessthan 5 μm and not more than 30 μm. It is preferable that the electrodefilm has a thickness which is not less than 0.5 μm and not more than 20μm.

It is preferable that the plurality of electrode films, which areincluded in the multilayered member for constructing thepiezoelectric/electrostrictive element, are stacked alternately, andthey are connected so that an identical voltage is applied to everyother layer.

Especially, when the thin plate section is made of metal, thepiezoelectric/electrostrictive element is formed such that only thepiezoelectric/electrostrictive layer of the first layer, or theelectrode film of the first layer and the piezoelectric/electrostrictivelayer of the first layer, of the multilayered member for constructingthe piezoelectric/electrostrictive element make contact with the thinplate section. By doing so, it is possible to avoid the phenomenon ofshort circuit formation between the different electrodes.

It is also preferable that one of ends of the electrode layer is formedat a position not including at least the fixation section as viewed inplan view. It is also preferable that an end of the multilayered memberfor constructing the piezoelectric/electrostrictive element is formed ata position not including at least the fixation section as viewed in planview.

It is preferable that (1−Lb/La) is not less than 0.4, provided that Larepresents a shortest distance concerning the pair of thin platesections between a boundary portion with respect to the object memberand a boundary portion with respect to the fixation section, and Lbrepresents a shortest distance of distances from the boundary portionbetween the thin plate section and one of the object member and thefixation section on which the multilayered member for constructing thepiezoelectric/electrostrictive element is not formed, to an end of theelectrode film. More preferably (1−Lb/La) is 0.5 to 0.8.

It is preferable that when the thin plate section is made of metal, thethin plate section is composed of a metal plate subjected to a coldrolling process.

It is also preferable that an adhesive, which has a thickness of notless than 0.1 μm and not more than 30 μm, is allowed to intervenebetween the thin plate section and the multilayered member forconstructing the piezoelectric/electrostrictive element. In thisarrangement, the adhesive may be organic resin, or the adhesive may beglass, brazing material, or solder.

It is also preferable that an underlying layer is formed on a surface ofthe multilayered member opposed to the thin plate section. It is alsopreferable that one or more holes or recesses are formed at least at aportion of the thin plate section at which the multilayered member isformed. In this arrangement, the adhesive enters the inside of the holeand the recess, and hence the adhesion area is substantially increased.Further, it is possible to use a thinner adhesive layer. It is alsopreferable that at least a portion of a surface of the thin platesection, on which the multilayered member is formed, is a rough surface.In this arrangement, the adhesion area is substantially increased, andhence the adhesion can be tightly effected. It is preferable that anadhesive, which has a thickness of not less than 0.1 μm and not morethan 30 μm, is allowed to intervene between the thin plate section andat least the fixation section. In this arrangement, the adhesive may beorganic resin, or the adhesive may be glass, brazing material, orsolder.

It is preferable that a stick-out shape of the adhesive, which protrudesfrom an opposing portion between the thin plate section and at least thefixation section, has a curvature. In this arrangement, the inner wallof the fixation section and the inner wall of each of the thin platesections are used as the adhesion surface. Therefore, the adhesion areais increased, and it is possible to increase the adhesion strength.Further, the concentration of the stress, which would be otherwisecaused on the joined portion (angular portion) between the inner wall ofthe fixation section and the inner wall of each of the thin platesections, can be effectively dispersed.

It is preferable that when an object member intervenes between open endsof the pair of thin plate sections, at least an angular portion of thefixation section opposed to the object member is chamfered. In thisarrangement, the stick-out amount of the adhesive can be stabilized byappropriately adjusting the chamfering angle and the radius ofcurvature. Further, it is possible to suppress the local dispersion ofthe adhesion strength. Thus, it is possible to improve the yield. It ispreferable that when the thin plate section is manufactured by means ofstamping for a metal plate, a burr, which is brought about by thestamping, is directed outwardly, considering the handling performanceand the direction of adhesion of the respective members.

According to still another aspect of the present invention, there isprovided a method for producing a piezoelectric/electrostrictive devicecomprising a pair of mutually opposing thin plate sections, and afixation section for supporting the thin plate sections; and one or morepiezoelectric/electrostrictive elements arranged on at least one thinplate section of the pair of thin plate sections; the method includesthe steps of preparing a plurality of thin plates for forming at leastthe thin plate sections thereafter, the piezoelectric/electrostrictiveelement, and a support substrate; securing thepiezoelectric/electrostrictive element to at least one of the thinplates by the aid of a first adhesive; securing the plurality of thinplates to the support substrate by the aid of a second adhesive tomanufacture a master device block including the plurality of thin platesdisposed opposingly; and dividing the master device block into aplurality of chips to manufacture individuals of thepiezoelectric/electrostrictive devices.

According to still another aspect of the present invention, there isprovided a method for producing a piezoelectric/electrostrictive deviceincluding a pair of mutually opposing thin plate sections, and afixation section for supporting the thin plate sections; and one or morepiezoelectric/electrostrictive elements arranged on at least one thinplate section of the pair of thin plate sections; the method includingthe steps of preparing a plurality of thin plates for forming at leastthe thin plate sections thereafter, the piezoelectric/electrostrictiveelement, and a support substrate; securing the plurality of thin platesto the support substrate by the aid of a second adhesive to manufacturea master device block including the plurality of thin plates disposedopposingly; securing the piezoelectric/electrostrictive element to atleast one of the thin plates by the aid of a first adhesive; anddividing the master device block into a plurality of chips tomanufacture individuals of the piezoelectric/electrostrictive devices.

According to the production methods as described above, it is possibleto easily produce the piezoelectric/electrostrictive device in which thepair of thin plate sections can be greatly displaced, and it is possibleto achieve realization of the high speed (realization of the highresonance frequency) of the device, especially of the displacementaction of the pair of thin plate sections.

It is also preferable in the production method described above that whenan object member intervenes between open ends of the pair of thin platesections of the piezoelectric/electrostrictive device to be produced;the support substrate is a rectangular annular structure having aportion to be formed into at least the object member thereafter, and aportion to be formed into the fixation section thereafter.

Alternatively, it is also preferable in the production method describedabove that when an object member does not intervene between open ends ofthe pair of thin plate sections of the piezoelectric/electrostrictivedevice to be produced; the support substrate is a rectangular annularstructure having a portion for supporting the open ends (portion tosubstantially define the thickness of a portion for allowing at leastthe object member to intervene thereafter), and a portion to be formedinto the fixation section thereafter.

The first adhesive and/or the second adhesive may be organic resin, orthe first adhesive and/or the second adhesive may be glass, brazingmaterial, or solder. On the other hand, the thin plates and/or thesupport substrate may be made of metal.

It is preferable that when the step of dividing the master device blockincludes a treatment for cutting the master device block alongpredetermined cutting lines; the cutting is performed in substantiallythe same direction as a displacement direction of the pair of thin platesections.

Further, it is also preferable that the production method according tothe present invention further includes the step of forming an underlyinglayer on a surface of the piezoelectric/electrostrictive element opposedto the thin plate before securing the piezoelectric/electrostrictiveelement to the thin plate by the aid of the first adhesive. It is alsopreferable that the production method according to the present inventionfurther includes the step of forming one or more holes or recesses atleast at a portion of the thin plate to which thepiezoelectric/electrostrictive element is secured.

It is also preferable that at least a portion of a surface of the thinplate, to which the piezoelectric/electrostrictive element is secured,is roughened. It is also preferable to form a curvature for a stick-outshape of the second adhesive protruding from an opposing portion betweenthe thin plate and the support substrate.

It is also preferable to chamfer mutually opposing angular portions ofthe support substrate of the master device block. It is also preferablethat the method further comprises the step of manufacturing the thinplate by means of stamping for a metal plate; wherein when the masterdevice block is produced by combining the thin plate with the supportsubstrate, a burr, which is brought about on the thin plate due to thestamping, is directed outwardly to produce the master device block.

Therefore, the piezoelectric/electrostrictive device according to thepresent invention can be utilized as the active device including, forexample, various transducers, various actuators, frequency regionfunctional parts (filters), transformers, vibrators, resonators,oscillators, and discriminators for the communication and the powergeneration, as well as the sensor element for various sensors including,for example, ultrasonic sensors, acceleration sensors, angular velocitysensors, shock sensors, and mass sensors. Especially, thepiezoelectric/electrostrictive device according to the present inventioncan be preferably utilized for various actuators to be used for themechanism for adjusting the displacement and the positioning and foradjusting the angle for various precision parts such as those of opticalinstruments and precision mechanical equipments.

The above and other objects, features, and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which a preferredembodiment of the present invention is shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a first embodiment;

FIG. 2 shows a perspective view illustrating a first modified embodimentof the piezoelectric/electrostrictive device according to the firstembodiment;

FIG. 3 shows a perspective view illustrating a second modifiedembodiment of the piezoelectric/electrostrictive device according to thefirst embodiment;

FIG. 4 shows a perspective view illustrating a third modified embodimentof the piezoelectric/electrostrictive device according to the firstembodiment;

FIG. 5 shows a perspective view illustrating a fourth modifiedembodiment of the piezoelectric/electrostrictive device according to thefirst embodiment;

FIG. 6 shows a perspective view illustrating a fifth modified embodimentof the piezoelectric/electrostrictive device according to the firstembodiment;

FIG. 7 shows a perspective view illustrating another embodiment of thepiezoelectric/electrostrictive device concerning the fifth modifiedembodiment;

FIG. 8 shows a perspective view illustrating a sixth modified embodimentof the piezoelectric/electrostrictive device according to the firstembodiment;

FIG. 9 shows a perspective view illustrating a seventh modifiedembodiment of the piezoelectric/electrostrictive device according to thefirst embodiment;

FIG. 10 shows, with partial omission, another embodiment of thepiezoelectric/electrostrictive element;

FIG. 11 shows, with partial omission, still another embodiment of thepiezoelectric/electrostrictive element;

FIG. 12 illustrates a situation in which both of thepiezoelectric/electrostrictive elements do not make the displacementaction in the piezoelectric/electrostrictive device according to thefirst embodiment;

FIG. 13A shows a waveform illustrating a voltage waveform to be appliedto the first piezoelectric/electrostrictive element;

FIG. 13B shows a waveform illustrating a voltage waveform to be appliedto the second piezoelectric/electrostrictive element;

FIG. 14 illustrates a situation in which thepiezoelectric/electrostrictive element makes the displacement action inthe piezoelectric/electrostrictive device according to the firstembodiment;

FIG. 15 shows a perspective view illustrating an arrangement in which asecond piezoelectric/electrostrictive device is secured to a movablesection of a first piezoelectric/electrostrictive device;

FIG. 16A illustrates a process for stacking necessary ceramic greensheets in a first production method;

FIG. 16B illustrates a state in which a ceramic green stack is formed;

FIG. 17A illustrates a state in which the ceramic green stack issintered to provide a ceramic stack;

FIG. 17B illustrates a state in which piezoelectric/electrostrictiveelements, which are constructed as separate members, are glued to thesurfaces of metal plates to serves as thin plate sections respectively;

FIG. 18 illustrates a state in the first production method in which themetal plate is glued to the ceramic stack to provide a hybrid stack;

FIG. 19 illustrates a state in which the hybrid stack is cut alongpredetermined cutting lines to provide thepiezoelectric/electrostrictive device according to the first embodiment;

FIG. 20A illustrates a process for stacking necessary ceramic greensheets in a second production method;

FIG. 20B illustrates a state in which a ceramic green stack is formed;

FIG. 21A illustrates a state in which the ceramic green stack issintered to provide a ceramic stack, and then a hole is filled with afiller material;

FIG. 21B illustrates a state in which metal plates to serve as thinplate sections respectively are glued to the ceramic stack to provide ahybrid stack;

FIG. 22 illustrates a state in which piezoelectric/electrostrictiveelements, which are constructed as separate members, are glued to thesurfaces of the metal plates of the hybrid stack;

FIG. 23 illustrates a state in which the piezoelectric/electrostrictivedevice according to the first embodiment is produced by cutting thehybrid stack along predetermined cutting lines;

FIG. 24 shows a perspective view illustrating an arrangement of apiezoelectric/electrostrictive device according to a second embodiment;

FIG. 25 shows a perspective view illustrating another arrangement of thepiezoelectric/electrostrictive device according to the secondembodiment;

FIG. 26 shows a magnified view illustrating an exemplary arrangement ofa stacked type piezoelectric/electrostrictive element;

FIG. 27 shows a magnified view illustrating a preferred exemplaryarrangement of the stacked type piezoelectric/electrostrictive elementshown in FIG. 26;

FIG. 28 shows a magnified view illustrating another exemplaryarrangement of a stacked type piezoelectric/electrostrictive element;

FIG. 29 shows a magnified view illustrating a preferred exemplaryarrangement of the stacked type piezoelectric/electrostrictive elementshown in FIG. 28;

FIG. 30 shows a perspective view illustrating still another arrangementof the piezoelectric/electrostrictive device according to the secondembodiment;

FIG. 31 illustrates the preferred dimensional relationship concerningthe piezoelectric/electrostrictive device according to the secondembodiment;

FIG. 32 illustrates a state in a third production method in which arectangular hole is bored through a central portion of a stainless steelplate to manufacture a substrate having a rectangular annular structure;

FIG. 33 illustrates a state in which an adhesive is formed on the firststainless steel thin plate;

FIG. 34 illustrates a state in which the stacked typepiezoelectric/electrostrictive element is glued to the first stainlesssteel thin plate with the adhesive intervening therebetween;

FIG. 35 illustrates a state in which the first and second stainlesssteel thin plates are glued to the substrate by the aid of the adhesive;

FIG. 36 illustrates a state in which a manufactured master device blockis cut;

FIG. 37 illustrates a state in a fourth production method in which arectangular hole is bored through a central portion of a stainless steelplate to manufacture a substrate having a rectangular annular structure,and first and second stainless steel-thin plates are glued to thesubstrate by the aid of an adhesive;

FIG. 38 illustrates a state in which the first and second stainlesssteel thin plates are glued by the aid of the adhesive;

FIG. 39 illustrates a state in which the adhesive is formed on the firststainless steel thin plate;

FIG. 40 illustrates a state in which a stacked typepiezoelectric/electrostrictive element is glued to the first stainlesssteel thin plate by the aid of the adhesive;

FIG. 41 illustrates a state in which first and second stainless steelthin plates are glued to another exemplary substrate by the aid of anadhesive;

FIG. 42 illustrates an example in which bumps are provided at portionsof respective stainless steel thin plates to which a support section tobe formed into a movable section thereafter and a support section to beformed into a fixation section thereafter are glued respectively;

FIG. 43 illustrates an example in which bumps are provided at portionsof respective stainless steel thin plates to which a support section tobe formed into a fixation section thereafter is glued;

FIG. 44 illustrates an example in which no bump is provided onrespective stainless steel thin plates;

FIG. 45 illustrates an example in which projections for formingcompartments for gluing are provided at portions of respective stainlesssteel thin plates to which a support section to be formed into a movablesection thereafter and a support section to be formed into a fixationsection thereafter are glued respectively;

FIG. 46 illustrates a case concerning the example shown in FIG. 42, inwhich the size of the support section to be formed into the fixationsection, especially the areal size of the surface of the stainless steelthin plate opposed to the bump is larger than the areal size of thebump;

FIG. 47 illustrates a first technique (to define holes through astainless steel thin plate);

FIG. 48 illustrates a second technique (to roughen the surfaces of astainless steel thin plate and a stacked typepiezoelectric/electrostrictive element);

FIG. 49 illustrates a third technique (to provide a curvature forstick-out portions of an adhesive);

FIG. 50 illustrates a fourth technique (to chamfer angular portions ofrespective support sections);

FIG. 51 illustrates a fifth technique (to direct burrs outwardly);

FIG. 52 illustrates a sixth technique (to change the thickness forrespective stainless steel thin plates); and

FIG. 53 shows an arrangement of a piezoelectric/electrostrictive deviceconcerning an illustrative conventional technique.

DETAILED DESCRIPTION OF THE INVENTION

Explanation will be made below with reference to FIGS. 1 to 52 forillustrative embodiments of the piezoelectric/electrostrictive deviceand the production method for the same according to the presentinvention.

It is noted that the piezoelectric/electrostrictive device resides in aconcept which includes the element for mutually converting the electricenergy and the mechanical energy by the aid of thepiezoelectric/electrostrictive element. Therefore, thepiezoelectric/electrostrictive device is most preferably used as theactive element such as various actuators and vibrators, especially asthe displacement element based on the use of the displacement broughtabout by the inverse piezoelectric effect or the electrostrictiveeffect. Additionally, the piezoelectric/electrostrictive device is alsopreferably used as the passive element such as acceleration sensorelements and shock sensor elements.

As shown in FIG. 1, the piezoelectric/electrostrictive device 10Aaccording to the first embodiment has a substrate 14 which has a lengthyrectangular parallelepiped-shaped configuration as a whole and which hasa hole 12 provided at an approximately central portion in the major axisdirection thereof.

The substrate 14 comprises a pair of mutually opposing thin platesections 16 a, 16 b, a movable section 20, and a fixation section 22 forsupporting the pair of thin plate sections 16 a, 16 b and the movablesection 20. Piezoelectric/electrostrictive elements 24 a, 24 b areformed at respective parts of at least the thin plate sections 16 a, 16b respectively.

The substrate 14 may be constructed by using ceramics or metal for theentire substrate 14. Alternatively, the substrate 14 may have a hybridstructure obtained by combining those produced with ceramic and metalmaterials. Further, those adoptable for constructing the substrate 14include, for example, a structure in which respective parts are glued toone another with an adhesive such as organic resin and glass, and ametal integrated structure which is integrated into one unit, forexample, by means of brazing, soldering, eutectic bonding, or welding.

In the first embodiment, the substrate 14 has a hybrid structure inwhich the pair of thin plate sections 16 a, 16 b are made of metal, andthe other parts, i.e., the movable section 20 and the fixation section22 are made of ceramics. Specifically, the thin plate sections 16 a, 16b made of metal are secured by an adhesive 200 to respective sidesurfaces of the movable section 20 and the fixation section 22 made ofceramics. It is a matter of course that all of the thin plate sections16 a, 16 b, the movable section 20, and the fixation section 22 may bemade of metal.

The piezoelectric/electrostrictive elements 24 a, 24 b are prepared asseparate members as described later on, and the preparedpiezoelectric/electrostrictive elements 24 a, 24 b are affixed to thesubstrate 14 with an adhesive such as organic resin or glass or by meansof brazing, soldering, or eutectic bonding. Alternatively, thepiezoelectric/electrostrictive elements 24 a, 24 b are directly formedon the substrate 14 by using the film formation method not by using thesticking method described above. In the first embodiment, thepiezoelectric/electrostrictive elements 24 a, 24 b are secured onto thethin plate sections 16 a, 16 b by the aid of an adhesive 202respectively.

The piezoelectric/electrostrictive device 10A includes the hole 12having, for example, a rectangular configuration which is formed by bothinner walls of the pair of thin plate sections 16 a, 16 b, an inner wall20 a of the movable section 20, and an inner wall 22 a of the fixationsection 22. The piezoelectric/electrostrictive device 10A is constructedsuch that the movable section 20 is displaced in accordance with thedriving of the piezoelectric/electrostrictive element or elements 24 aand/or 24 b, or the displacement of the movable section 20 is detectedby the piezoelectric/electrostrictive element or elements 24 a and/or 24b.

Each of the piezoelectric/electrostrictive elements 24 a, 24 b includesa piezoelectric/electrostrictive layer 26, and a pair of electrodes 28,30 formed on both sides of the piezoelectric/electrostrictive layer 26.One electrode 28 of the pair of electrodes 28, 30 is formed at least oneach of the pair of thin plate sections 16 a, 16 b.

In the embodiment shown in FIG. 1, respective forward end surfaces ofthe pair of electrodes 28, 30 and the piezoelectric/electrostrictivelayer 26 for constructing the piezoelectric/electrostrictive element 24a, 24 b are substantially aligned. A substantial driving portion 18 ofthe piezoelectric/electrostrictive element 24 a, 24 b (portion at whichthe pair of electrodes 28, 30 are overlapped with each other with thepiezoelectric/electrostrictive layer 26 interposed therebetween) iscontinuously formed over a range from a part of the outercircumferential surface of the fixation section 22 to a part of theouter circumferential surface of the thin plate section 16 a, 16 b.Especially, in this embodiment, the respective forward end surfaces ofthe pair of electrodes 28, 30 are located at the positions slightlydeviated rearwardly from the inner wall 20 a of the movable section 20.Of course, the piezoelectric/electrostrictive element 24 a, 24 b may beformed such that the substantial driving portion 18 is located over arange from a part of the movable section 20 to a part of the thin platesection 16 a, 16 b.

As shown in FIG. 1, the piezoelectric/electrostrictive device 10Aaccording to the first embodiment described above includes mutuallyopposing end surfaces 36 a, 36 b which are formed in the movable section20. Each of the end surfaces 36 a, 36 b is a surface substantiallyparallel to the side surface of the movable section 20, i.e., thesurface for forming the element. The respective end surfaces 36 a, 36 bare separated from each other from the upper surface of the movablesection 20 to the hole 12. In this arrangement, as shown in FIG. 12, forexample, it is preferable that the distances Da, Db, which range fromthe central axis n of the movable section 20 to the respective endsurfaces 36 a, 36 b, are substantially equal to one another.

As shown in FIG. 1, for example, a gap (air) 38 may be allowed tointervene between the end surfaces 36 a, 36 b. Alternatively, as in apiezoelectric/electrostrictive device 10Ag according to a seventhmodified embodiment shown in FIG. 9 or as shown in FIG. 12, a memberdifferent from the constitutive member of the movable section 20, forexample, a member 40 composed of, for example, resin or the like may beallowed to intervene between the end surfaces 36 a, 36 b.

In the piezoelectric/electrostrictive device 10A according to the firstembodiment, the voltage is applied to the pair of electrodes 28, 30 viaterminals (pads) 32, 34 of the respective electrodes 28, 30 formed onboth side surfaces (element formation surfaces) of the fixation section22 respectively. The respective terminals 32, 34 are positioned asfollows. That is, the terminal 32 corresponding to the first electrode28 is formed at the position deviated toward the rearward end of thefixation section 22. The terminal 34 corresponding to the secondelectrode 30 disposed on the side of the external space is formed at theposition deviated toward the inner wall 22 a of the fixation section 22.

In this embodiment, the piezoelectric/electrostrictive device 10A can beindividually fixed by utilizing the surfaces respectively different fromthe surfaces on which the terminals 32, 34 are arranged. As a result, itis possible to obtain the high reliability for both of the fixation ofthe piezoelectric/electrostrictive device 10A and the electricconnection between the circuit and the terminals 32, 34. In thisarrangement, the electric connection between the terminals 32, 34 andthe circuit is made, for example, by means of the flexible printedcircuit (also referred to as FPC), the flexible flat cable (alsoreferred to as FFC), and the wire bonding.

Structures other than the structure shown in FIG. 1 are available toconstruct the piezoelectric/electrostrictive element 24 a, 24 b. Thatis, as in a piezoelectric/electrostrictive device 10Aa according to afirst modified embodiment shown in FIG. 2, it is also preferable thatthe respective forward ends of the pair of electrodes 28, 30 forconstructing the piezoelectric/electrostrictive element 24 a, 24 b arealigned, and only the forward end of the piezoelectric/electrostrictivelayer 26 is allowed to protrude toward the movable section 20.Alternatively, as in a piezoelectric/electrostrictive device 10Abaccording to a second modified embodiment shown in FIG. 3, it is alsopreferable that the respective forward ends of the first electrode 28and the piezoelectric/electrostrictive layer 26 are aligned, and onlythe forward end of the second electrode 30 is disposed at a positiondeviated toward the fixation section 22. Thepiezoelectric/electrostrictive device 10Ab shown in FIG. 3 isillustrative of the case in which mutually opposing end surfaces 36 a,36 b are provided in the fixation section 22 in place of the movablesection 20.

Alternatively, as in a piezoelectric/electrostrictive device 10Acaccording to a third modified embodiment shown in FIG. 4, it is alsopreferable that the respective forward ends of the first electrode 28and the piezoelectric/electrostrictive layer 26 are allowed to extend upto the side surface of the movable section 20, and the forward end ofthe second electrode 30 is located at an approximately central portionin the length direction (Z axis direction) of the thin plate section 16a, 16 b.

In the embodiments described above, the piezoelectric/electrostrictiveelement 24 a, 24 b is constructed by the piezoelectric/electrostrictivelayer 26 having the one-layered structure and the pair of electrodes 28,30. Alternatively, it is also preferable that thepiezoelectric/electrostrictive element 24 a, 24 b is constructed in astacked form composed of a plurality of units each comprising thepiezoelectric/electrostrictive layer 26 and the pair of electrodes 28,30.

For example, as in a piezoelectric/electrostrictive device 10Adaccording to a fourth modified embodiment shown in FIG. 5, each of thepiezoelectric/electrostrictive layer 26 and the pair of electrodes 28,30 resides in a multilayered structure. The first electrodes 28 and thesecond electrodes 30 are alternately stacked with each other to providethe piezoelectric/electrostrictive element 24 a, 24 b which has amultiple stage structure at a portion (substantial driving portion 18)at which the first electrodes 28 and the second electrodes 30 areoverlapped with each other with the piezoelectric/electrostrictive layer26 interposed therebetween. FIG. 5 is illustrative of the followingcase. That is, the piezoelectric/electrostrictive layer 26 has thethree-layered structure. The first electrodes 28 are formed in aseparate manner respectively on the lower surface of the first layer(side surface of the thin plate section 16 a, 16 b) and on the uppersurface of the second layer. The second electrodes 30 are formed in aseparate manner respectively on the upper surface of the first layer andon the upper surface of the third layer. Further, terminals 32 a, 32 bare provided on respective ends of the first electrodes 28 respectively,and terminals 34 a, 34 b are provided on respective ends of the secondelectrodes 30 respectively.

As in a piezoelectric/electrostrictive device 10Ae according to a fifthmodified embodiment shown in FIG. 6, each of thepiezoelectric/electrostrictive layer 26 and the pair of electrodes 28,30 resides in a multilayered structure. The first electrode 28 and thesecond electrode 30 are alternately stacked with each other so that asubstantially comb-shaped configuration is obtained in cross section toprovide the piezoelectric/electrostrictive element 24 a, 24 b which hasa multiple stage structure at a portion (substantial driving portion 18)at which the first electrode 28 and the second electrode 30 areoverlapped with each other with the piezoelectric/electrostrictive layer26 interposed therebetween. FIG. 6 is illustrative of the followingcase. That is, the piezoelectric/electrostrictive layer 26 has thethree-layered structure. The first electrode 28 is formed in acomb-shaped configuration to be located on the lower surface of thefirst layer (side surface of the thin plate section 16 a, 16 b) and onthe upper surface of the second layer. The second electrode 30 is formedin a comb-shaped configuration to be located on the upper surface of thefirst layer and on the upper surface of the third layer. In the case ofthis structure, each of the first electrode 28 and the second electrode30 is continuous and common. Accordingly, it is possible to decrease thenumber of terminals 32, 34 as compared with the structure shown in FIG.5. Therefore, it is possible to suppress the increase in size whichwould be otherwise involved in the multilayered structure of thepiezoelectric/electrostrictive element 24 a, 24 b.

Another example of the piezoelectric/electrostrictive device 10Aeaccording to the fifth embodiment is shown in FIG. 7. In this case, itis also preferable to form the piezoelectric/electrostrictive element 24a, 24 b so that the forward end thereof stays on the thin plate section16 a, 16 b. FIG. 7 is illustrative of the case in which the forward endof the piezoelectric/electrostrictive element 24 a, 24 b is located at asubstantially central portion in the length direction of the thin platesection. This arrangement is advantageous in that the movable section 20can be displaced to a great extent.

Alternatively, as in a piezoelectric/electrostrictive device 10Afaccording to a sixth modified embodiment shown in FIG. 8, it is alsopreferable that two piezoelectric/electrostrictive elements 24 a 1, 24 b1 having the multiple stage structure are formed to extend over thefixation section 22 and the thin plate section 16 a, 16 b respectively,and another two piezoelectric/electrostrictive elements 24 a 2, 24 b 2having the multiple stage structure are formed to extend over themovable section 20 and the thin plate section 16 a, 16 b respectively.In this arrangement, the movable section 20 can be displaced extremelygreatly owing to the effect that the piezoelectric/electrostrictiveelement 24 a, 24 b has the multiple stage structure and the effect thatthe number of points of action to displace the movable section 20 isincreased. Further, the piezoelectric/electrostrictive device 10Af isexcellent in high speed response performance, which is preferred.

Alternatively, as in a piezoelectric/electrostrictive device 10Agaccording to a seventh modified embodiment shown in FIG. 9, it is alsopreferable that the piezoelectric/electrostrictive layer 26 has thetwo-layered structure to provide the piezoelectric/electrostrictiveelement 24 a, 24 b having the multiple stage structure which is formedsuch that the first electrode 28 is located on the lower surface of thefirst layer (side surface of the thin plate section 16 a, 16 b) and onthe upper surface of the second layer, and the second electrode 30 islocated on the upper surface of the first layer. In this embodiment, thespace between the end surfaces 36 a, 36 b of the movable section 20 isfilled with a member which is different from the movable section 20.

The multiple stage structure of the piezoelectric/electrostrictiveelement 24 a, 24 b as described above increases the force generated bythe piezoelectric/electrostrictive element 24 a, 24 b, and thus it ispossible to obtain the large displacement. Further, the rigidity of thepiezoelectric/electrostrictive device 10A itself is increased, and thusit is possible to realize the high resonance frequency. It is possibleto achieve the high speed displacement action with ease.

When the number of stages is increased, it is possible to increase thedriving force. However, the electric power consumption is also increasedin accordance therewith. Therefore, when the device is practicallyproduced and used, for example, it is preferable that the number ofstages is appropriately determined depending on the way of use and thestate of use. In the case of the piezoelectric/electrostrictive device10A according to the first embodiment, even when the driving force isincreased by providing the multiple stage structure of thepiezoelectric/electrostrictive element 24 a, 24 b, the width of the thinplate section 16 a, 16 b (distance in the Y axis direction) is basicallyunchanged. Therefore, the device is extremely preferred to makeapplication, for example, to the actuator for the purpose of the ringingcontrol and the positioning of the magnetic head for the hard disk to beused in an extremely narrow gap. Further, when the device is used as asensor (for example, an acceleration sensor), the device provides thefollowing advantage, because the electrostatic capacity is increased,and the generated electric charge is increased, owing to the multiplestage structure. That is, the level of the electric signal generated bythe sensor is increased, and it is easy to perform the processing in asignal processing circuit to be connected to the downstream stage of thesensor.

The piezoelectric/electrostrictive element 24 a, 24 b is illustrative ofthe case of the so-called sandwich structure in which thepiezoelectric/electrostrictive layer 26 is interposed between the pairof electrodes 28, 30. Alternatively, as shown in FIG. 10, a pair ofcomb-shaped electrodes 28, 30 may be formed on the first principalsurface of the piezoelectric/electrostrictive layer 26 formed on atleast the side surface of the thin plate section 16 a, 16 b. Furtheralternatively, as shown in FIG. 11, a pair of comb-shaped electrodes 28,30 are formed and embedded in the piezoelectric/electrostrictive layer26 formed on at least the side surface of the thin plate section 16 a,16 b.

The structure shown in FIG. 10 is advantageous in that it is possible tosuppress the electric power consumption to be low. The structure shownin FIG. 11 makes it possible to effectively utilize the inversepiezoelectric effect in the direction of the electric field having largegenerated force and strain, which is advantageous to cause the largedisplacement.

Specifically, the piezoelectric/electrostrictive element 24 a, 24 bshown in FIG. 10 comprises the pair of electrodes 28, 30 having thecomb-shaped structure formed on the first principal surface of thepiezoelectric/electrostrictive layer 26. In this structure, the firstelectrode 28 and the second electrode 30 are mutually opposed to oneanother in an alternate manner with a gap 29 having a constant widthinterposed therebetween. FIG. 10 is illustrative of the case in whichthe pair of electrodes 28, 30 are formed on the first principal surfaceof the piezoelectric/electrostrictive layer 26. Alternatively, the pairof electrodes 28, 30 may be formed between the thin plate section 16 a,16 b and the piezoelectric/electrostrictive layer 26. Furtheralternatively, the pair of comb-shaped electrodes 28, 30 may be formedon the first principal surface of the piezoelectric/electrostrictivelayer 26 and between the thin plate section 16 a, 16 b and thepiezoelectric/electrostrictive layer 26 respectively.

On the other hand, in the piezoelectric/electrostrictive element 24 a,24 b shown in FIG. 11, the pair of electrodes 28, 30 having thecomb-shaped structure are formed so that they are embedded in thepiezoelectric/electrostrictive layer 26. In this structure, the firstelectrode 28 and the second electrode 30 are mutually opposed to oneanother in an alternate manner with a gap 29 having a constant widthinterposed therebetween.

The piezoelectric/electrostrictive elements 24 a, 24 b as shown in FIGS.10 and 11 can be preferably used for the piezoelectric/electrostrictivedevice 10A according to the first embodiment as well. When the pair ofcomb-shaped electrodes 28, 30 are used as in thepiezoelectric/electrostrictive elements 24 a, 24 b shown in FIGS. 10 and11, the displacement of the piezoelectric/electrostrictive element 24 a,24 b can be increased by decreasing the pitch D of the comb teeth of therespective electrodes 28, 30.

The operation of the piezoelectric/electrostrictive device 10A accordingto the first embodiment will now be explained. At first, for example,when the two piezoelectric/electrostrictive elements 24 a, 24 b are inthe natural state, namely when both of thepiezoelectric/electrostrictive elements 24 a, 24 b do not make thedisplacement action, then the major axis m of thepiezoelectric/electrostrictive device 10A (major axis of the fixationsection) is substantially coincident with the central axis n of themovable section 20 as shown in FIG. 12.

Starting from this state, for example, a sine wave Wa, which has apredetermined bias electric potential Vb, is applied to the pair ofelectrodes 28, 30 of the first piezoelectric/electrostrictive element 24a as shown in a waveform figure shown in FIG. 13A, while a sine wave Wb,which has a phase different from that of the sine wave Wa by about 180°,is applied to the pair of electrodes 28, 30 of the secondpiezoelectric/electrostrictive element 24 b as shown in FIG. 13B.

The piezoelectric/electrostrictive layer 26 of the firstpiezoelectric/electrostrictive element 24 a makes the contractiondisplacement in the direction of the first principal surface at a stageat which, for example, a voltage having a maximum value is applied tothe pair of electrodes 28, 30 of the firstpiezoelectric/electrostrictive element 24 a. Accordingly, as shown inFIG. 14, for example, the stress is generated for the first thin platesection 16 a to bend the thin plate section 16 a, for example, in therightward direction as shown by the arrow A. Therefore, the first thinplate section 16 a is bent in the rightward direction. At this time, astate is given, in which no voltage is applied to the pair of electrodes28, 30 of the second piezoelectric/electrostrictive element 24 b.Therefore, the second thin plate section 16 b follows the bending of thefirst thin plate section 16 a, and it is bent in the rightwarddirection. As a result, the movable section 20 is displaced, forexample, in the rightward direction with respect to the major axis m ofthe piezoelectric/electrostrictive device 10A. The displacement amountis changed depending on the maximum value of the voltage applied to eachof the piezoelectric/electrostrictive elements 24 a, 24 b. For example,the larger the maximum value is, the larger the displacement amount is.

Especially, when a material having high coercive electric field isapplied as the constitutive material for thepiezoelectric/electrostrictive layer 26, it is also preferable that thebias electric potential is adjusted so that the level of the minimumvalue is a slightly negative level as depicted by waveforms indicated bytwo-dot chain lines in FIGS. 13A and 13B. In this case, for example, thestress, which is in the same direction as the bending direction of thefirst thin plate section 16 a, is generated in the second thin platesection 16 b by driving the piezoelectric/electrostrictive element (forexample, the second piezoelectric/electrostrictive element 24 b) towhich the negative level is applied. Accordingly, it is possible tofurther increase the displacement amount of the movable section 20. Inother words, when the waveforms indicated by the dashed lines in FIGS.13A and 13B are used, the device is allowed to have such a function thatthe piezoelectric/electrostrictive element 24 b or 24 a, to which thenegative level is applied, supports the piezoelectric/electrostrictiveelement 24 a or 24 b which principally makes the displacement action.

In the case of the piezoelectric/electrostrictive device 10Af shown inFIG. 8, the voltage (see the sine waveform Wa) shown in FIG. 13A isapplied, for example, to the piezoelectric/electrostrictive element 24 a1 and the piezoelectric/electrostrictive element 24 b 2 which arearranged on the diagonal line, and the voltage (see the sine waveformWb) shown in FIG. 13B is applied to the otherpiezoelectric/electrostrictive element 24 a 2 and the otherpiezoelectric/electrostrictive element 24 b 1.

As described above, in the piezoelectric/electrostrictive device 10Aaccording to the first embodiment, the minute displacement of thepiezoelectric/electrostrictive element 24 a, 24 b is amplified into thelarge displacement action by utilizing the bending of the thin platesection 16 a, 16 b, and it is transmitted to the movable section 20.Accordingly, it is possible to greatly displace the movable section 20with respect to the major axis m of the piezoelectric/electrostrictivedevice 10A.

Especially, in the first embodiment, the movable section 20 is providedwith the mutually opposing end surfaces 36 a, 36 b. In this arrangement,the gap 38 is provided between the mutually opposing end surfaces 36 a,36 b, or the member 40, which is lighter than the constitutive member ofthe movable section 20, is allowed to intervene between the mutuallyopposing end surfaces 36 a, 36 b. Accordingly, it is possible toeffectively realize the light weight of the movable section 20. Thus, itis possible to increase the resonance frequency without decreasing thedisplacement amount of the movable section 20.

The frequency herein indicates the frequency of the voltage waveformobtained when the movable section 20 is displaced rightwardly andleftwardly by alternately switching the voltage applied to the pair ofelectrodes 28, 30. The resonance frequency indicates the frequency atwhich the displacement action of the movable section 20 is maximum whenthe predetermined sine wave voltage is applied.

In the piezoelectric/electrostrictive device 10A according to the firstembodiment, the hybrid structure is provided, in which the pair of thinplate sections 16 a, 16 b are made of metal, and the other components,i.e., the movable section 20 and the fixation section 22 are made ofceramics. It is unnecessary that all of the parts are formed with thepiezoelectric/electrostrictive material which is a fragile materialhaving a relatively heavy weight. Therefore, the device has thefollowing advantages. That is, the device has high mechanical strength,and it is excellent in handling performance, shock resistance, andmoisture resistance. Further, the operation of the device is scarcelyaffected by harmful vibration (for example, noise vibration andremaining vibration during high speed operation).

Further, in this embodiment, when the gap 38 is formed between themutually opposing end surfaces 36 a, 36 b, the part 20A of the movablesection 20 including the first end surface 36 a and the another part 20Bof the movable section 20 including the second end surface 36 b areeasily bent, resulting in strong resistance to the deformation.Accordingly, the piezoelectric/electrostrictive device 10A is excellentin handling performance.

The surface area of the movable section 20 or the fixation section 22 isincreased owing to the presence of the mutually opposing end surfaces 36a, 36 b. Therefore, as shown in FIG. 1, when the movable section 20 hasthe mutually opposing end surfaces 36 a, 36 b, the attachment area canbe increased when another part is attached to the movable section 20.Thus, it is possible to improve the attachment performance for the part.It is now assumed that the part is secured, for example, with anadhesive or the like. In this case, the adhesive is fully distributed tothe end surfaces 36 a, 36 b as well as to the first principal surface(attachment surface for the part) of the movable section 20. Therefore,it is possible to dissolve, for example, shortage of application of theadhesive. Thus, it is possible to reliably secure the part.

As an example of such an arrangement, FIG. 15 is illustrative of a casein which another piezoelectric/electrostrictive device according to theembodiment of the present invention (secondpiezoelectric/electrostrictive device 10A2) is secured to the movablesection 20 of the piezoelectric/electrostrictive device according to theembodiment of the present invention (firstpiezoelectric/electrostrictive device 10A1).

The first piezoelectric/electrostrictive device 10A1 has its fixationsection 22 which is secured to the surface of a base plate 122 by theaid of an adhesive 120. The fixation section 22 of the secondpiezoelectric/electrostrictive device 10A2 is secured to the movablesection 20 of the first piezoelectric/electrostrictive device 10A1 bythe aid of an adhesive 124. That is, in this arrangement, the twopiezoelectric/electrostrictive devices 10A1, 10A2 are arranged inseries. A member 126 having a light weight, which is different from themovable section 20, is allowed to intervene between the mutuallyopposing end surfaces 36 a, 36 b of the movable section 20 of the secondpiezoelectric/electrostrictive device 10A2.

In this case, the adhesive 124 for gluing the secondpiezoelectric/electrostrictive device 10A2 is fully distributed up tothe space between the end surfaces 36 a, 36 b of the movable section 20of the first piezoelectric/electrostrictive device 10A1. Accordingly,the second piezoelectric/electrostrictive device 10A2 is tightly securedto the first piezoelectric/electrostrictive device 10A1. When thepiezoelectric/electrostrictive device 10A2 is glued as described above,the light weight member (adhesive 124 in this case), which is differentfrom the movable section 20, is allowed to intervene between the endsurfaces 36 a, 36 b simultaneously with the adhesion. Therefore, thisarrangement is advantageous in that the production step can besimplified.

On the other hand, as shown in FIG. 3, when the fixation section 22 hasthe mutually opposing end surfaces 36 a, 36 b, it is possible to tightlyfix the piezoelectric/electrostrictive device 10Ab according to thesecond modified embodiment to a predetermined fixation portion, inaddition to the effect obtained when the movable section 20 has themutually opposing end surfaces 36 a, 36 b as described above. Thus, itis possible to improve the reliability.

In the first embodiment, the portion (substantial driving portion 18),at which the pair of electrodes 28, 30 are overlapped with each otherwith the piezoelectric/electrostrictive layer 26 interposedtherebetween, is continuously formed over the range from the part of thefixation section 22 to the part of the thin plate section 16 a, 16 b. Ifthe substantial driving portion 18 is formed to further extend over apart of the movable section 20, then it is feared that the displacementaction of the movable section 20 is restricted by the substantialdriving portion 18, and it is impossible to obtain the largedisplacement. However, in this embodiment, the substantial drivingportion 18 is formed such that it does not range over the movablesection 20. Therefore, it is possible to avoid the inconvenience of therestriction of the displacement action of the movable section 20, and itis possible to increase the displacement amount of the movable section20.

On the other hand, when the piezoelectric/electrostrictive element 24 a,24 b is formed on the part of the movable section 20, it is preferablethat the substantial driving portion 18 is located over the range fromthe part of the movable section 20 to the part of the thin plate section16 a, 16 b, because of the following reason. That is, if the substantialdriving portion 18 is formed to extend up to a part of the fixationsection 22, the displacement action of the movable section 20 isrestricted as described above.

Next, explanation will be made for preferred illustrative constructionsof the piezoelectric/electrostrictive device 10A according to the firstembodiment.

At first, in order to ensure the displacement action of the movablesection 20, it is preferable that the distance g, by which thesubstantial driving portion 18 of the piezoelectric/electrostrictiveelement 24 a, 24 b is overlapped with the fixation section 22 or themovable section 20, is not less than ½ of the thickness d of the thinplate section 16 a, 16 b.

The device is constructed such that the ratio a/b between the distance(distance in the X axis direction) a between the inner walls of the thinplate sections 16 a, 16 b and the width (distance in the Y axisdirection) b of the thin plate section 16 a, 16 b is 0.5 to 20. Theratio a/b is preferably 1 to 15 and more preferably 1 to 10. Theprescribed value of the ratio a/b is prescribed on the basis of thediscovery that the displacement amount of the movable section 20 isincreased to makes it possible to dominantly obtain the displacement inthe X-Z plane.

On the other hand, it is desirable that the ratio e/a between the length(distance in the Z axis direction) e of the thin plate section 16 a, 16b and the distance a between the inner walls of the thin plate sections16 a, 16 b is preferably 0.5 to 10 and more preferably 0.5 to 5.

Further, it is preferable that the hole 12 is filled with a gelmaterial, for example, silicon gel. Usually, the displacement action ofthe movable section 20 is restricted by the presence of such a fillermaterial. However, in the first embodiment, it is intended to realizethe light weight brought about by the formation of the end surfaces 36a, 36 b on the movable section 20 and increase the displacement amountof the movable section 20. Therefore, the restriction of thedisplacement action of the movable section 20 due to the filler materialis counteracted. Accordingly, it is possible to realize the effect owingto the presence of the filler material, namely the realization of thehigh resonance frequency and the maintenance of the rigidity.

It is preferable that the length (distance in the Z axis direction) f ofthe movable section 20 is short, because of the following reason. Thatis, it is possible to realize the light weight and increase theresonance frequency by shortening the length. However, in order toensure the rigidity of the movable section 20 in the X axis directionand obtain its reliable displacement, it is desirable that the radio f/dwith respect to the thickness d of the thin plate section 16 a, 16 b isnot less than 2, and preferably not less than 5.

The actual size of each component is determined considering, forexample, the joining area for attaching the part to the movable section20, the joining area for attaching the fixation section 22 to anothermember, the joining area for attaching the electrode terminal or thelike, and the strength, the durability, the necessary displacementamount, the resonance frequency, and the driving voltage of the entirepiezoelectric/electrostrictive device 10A.

Specifically, for example, the distance a between the inner walls of thethin plate sections 16 a, 16 b is preferably 100 μm to 2000 μm and morepreferably 200 μm to 1600 μm. The width b of the thin plate section 16a, 16 b is preferably 50 μm to 2000 μm and more preferably 100 μm to 500μm. The thickness d of the thin plate section 16 a, 16 b is preferably 2μm to 100 μm and more preferably 10 μm to 80 μm, while it satisfies b>din relation to the width b of the thin plate section 16 a, 16 b, inorder to make it possible to effectively suppress the swayingdisplacement which is the displacement component in the Y axisdirection.

The length e of the thin plate section 16 a, 16 b is preferably 200 μmto 3000 μm and more preferably 300 μm to 2000 μm. The length f of themovable section 20 is preferably 50 μm to 2000 μm and more preferably100 μm to 1000 μm.

The arrangement as described above exhibits such an extremely excellenteffect that the displacement in the Y axis direction does not exceeds10% with respect to the displacement in the X axis direction, while thedevice can be driven at a low voltage by appropriately making adjustmentwithin the range of the size range and the actual size, and it ispossible to suppress the displacement component in the Y axis directionto be not more than 5%. In other words, the movable section 20 isdisplaced in one axis direction, i.e., substantially in the X axisdirection. Further, the high speed response is excellent, and it ispossible to obtain the large displacement at a relatively low voltage.

In the piezoelectric/electrostrictive device 10A, the shape of thedevice is not the plate-shaped configuration (thickness is small in thedirection perpendicular to the displacement direction) unlikeconventional one. Each of the movable section 20 and the fixationsection 22 has the approximately rectangular parallelepiped-shapedconfiguration. The pair of thin plate sections 16 a, 16 b are providedso that the side surface of the movable section 20 is continuous to theside surface of the fixation section 22. Therefore, it is possible toselectively increase the rigidity of piezoelectric/electrostrictivedevice 10A in the Y axis direction.

That is, in the piezoelectric/electrostrictive device 10A, it ispossible to selectively generate only the operation of the movablesection 20 in the plane (XZ plane). It is possible to suppress theoperation of the movable section 20 in the YZ plane (operation in theso-called swaying direction).

Next, explanation will be made for the respective constitutivecomponents of the piezoelectric/electrostrictive device 10A according tothe first embodiment.

As described above, the movable section 20 is the portion which isoperated on the basis of the driving amount of the thin plate section 16a, 16 b, and a variety of members are attached thereto depending on thepurpose of use of the piezoelectric/electrostrictive device 10A. Forexample, when the piezoelectric/electrostrictive device 10A is used as adisplacement element, a shield plate for an optical shutter or the likeis attached thereto. Especially, when the piezoelectric/electrostrictivedevice 10A is used for the mechanism for positioning a magnetic head ofa hard disk drive or for suppressing the ringing, a member required tobe positioned is attached thereto, including, for example, the magnetichead, a slider provided with the magnetic head, and a suspensionprovided with the slider.

As described above, the fixation section 22 is the portion forsupporting the thin plate sections 16 a, 16 b and the movable section20. For example, in the case of the utilization to position the magnetichead of the hard disk drive, the entire piezoelectric/electrostrictivedevice 10A is fixed by supporting and securing the fixation section 22,for example, to a carriage arm attached to VCM (voice coil motor) or afixation plate or a suspension attached to the carriage arm. As shown inFIG. 1, the terminals 32, 34 for driving thepiezoelectric/electrostrictive elements 24 a, 24 b and other members arearranged on the fixation section 22 in some cases.

The material for constructing the movable section 20 and the fixationsection 22 is not specifically limited provided that it has rigidity.However, it is possible to preferably use ceramics to which the ceramicgreen sheet-stacking method is applicable as described later on.Specifically, the material includes, for example, materials containing amajor component of zirconia represented by stabilized zirconia andpartially stabilized zirconia, alumina, magnesia, silicon nitride,aluminum nitride, and titanium oxide, as well as materials containing amajor component of a mixture of them. However, in view of the highmechanical strength and the high toughness, it is preferable to use amaterial containing a major component of zirconia, especially stabilizedzirconia and a material containing a major component of partiallystabilized zirconia. The metal material is not limited provided that ithas rigidity. However, the metal material includes, for example,stainless steel, nickel, brass, cupronickel, and bronze.

Those which are stabilized or partially stabilized as follows arepreferably used as stabilized zirconia or partially stabilized zirconiaas described above. That is, the compound to be used for stabilizing orpartially stabilizing zirconia includes yttrium oxide, ytterbium oxide,cerium oxide, calcium oxide, and magnesium oxide. When at least onecompound of them is added and contained, zirconia is partially or fullystabilized. However, as for the stabilization, the objective zirconiacan be stabilized not only by adding one type of the compound but alsoby adding a combination of the compounds.

The amount of addition of each of the compounds is desirably as follows.That is, yttrium oxide or ytterbium oxide is added by 1 to 30 mole %,preferably 1.5 to 10 mole %. Cerium oxide is added by 6 to 50 mole %,preferably 8 to 20 mole %. Calcium oxide or magnesium oxide is added by5 to 40 mole %, preferably 5 to 20 mole %. Especially, it is preferableto use yttrium oxide as a stabilizer. In this case, yttrium oxide isdesirably added by 1.5 to 10 mole %, more preferably 2 to 4 mole %. Forexample, alumina, silica, or transition metal oxide may be added as anadditive of sintering aid or the like in a range of 0.05 to 20% byweight. However, when the sintering integration based on the filmformation method is adopted as a technique for forming thepiezoelectric/electrostrictive element 24 a, 24 b, it is also preferableto add, for example, alumina, magnesia, and transition metal oxide as anadditive.

In order to obtain the mechanical strength and the stable crystal phase,it is desirable that the average crystal grain size of zirconia is 0.05to 3 μm, preferably 0.05 to 1 μm. As described above, ceramics can beused for the thin plate section 16 a, 16 b in the same manner as in themovable section 20 and the fixation section 22. Preferably, it isadvantageous to construct the thin plate sections 16 a, 16 b with asubstantially identical material in view of the reliability of thejoined portion and the strength of the piezoelectric/electrostrictivedevice 10A in order to reduce any complicated procedure of theproduction.

As described above, the thin plate section 16 a, 16 b is the portionwhich is driven in accordance with the displacement of thepiezoelectric/electrostrictive element 24 a, 24 b. The thin platesection 16 a, 16 b is the thin plate-shaped member having flexibility,and it functions to amplify the expansion and contraction displacementof the piezoelectric/electrostrictive element 24 a, 24 b arranged on thesurface as the bending displacement and transmit the displacement to themovable section 20. Therefore, it is enough that the shape or thematerial of the thin plate section 16 a, 16 b provides the flexibilitywith the mechanical strength of such a degree that it is not broken bythe bending displacement. It is possible to make appropriate selectionconsidering the response performance and the operability of the movablesection 20.

It is preferable that the thickness d of the thin plate section 16 a, 16b is preferably about 2 μm to 100 μm. It is preferable that the combinedthickness of the thin plate section 16 a, 16 b and thepiezoelectric/electrostrictive element 24 a, 24 b is 7 μm to 500 μm. Itis preferable that the thickness of the electrode 28, 30 is 0.1 to 50μμm, and the thickness of the piezoelectric/electrostrictive layer 26 is3 to 300 μm. The width b of the thin plate section 16 a, 16 b ispreferably 50 μm to 2000 μm.

On the other hand, as for the shape and the material for the thin platesection 16 a, 16 b, it is enough to use those having the flexibility andhaving the mechanical strength of such a degree that no breakage occursdue to the bending displacement. Metal is preferably used. In this case,as described above, it is preferable to use a metal material which hasthe flexibility and which is capable of the bending displacement.Specifically, it is preferable to use a metal material which has aYoung's modulus of not less than 100 GPa.

Preferably, it is desirable that the thin plate section 16 a, 16 b ismade of an iron-based material such as various spring steel materials,marageing stainless steel materials, and stainless steel materialsincluding, for example, austenite-based stainless steel materials suchas SUS301, SUS304, AISI653, and SUH660, ferrite-based stainless steelmaterials such as SUS430 and SUS434, maltensite-based stainless steelmaterials such as SUS410 and SUS630, and semiaustenite-based stainlesssteel materials such as SUS631 and AISI632. Alternatively, it isdesirable that the thin plate section 16 a, 16 b is made of anon-ferrous material such as superelastic titanium alloy represented bytitanium-nickel alloy, brass, cupronickel, aluminum, tungsten,molybdenum, beryllium copper, phosphor bronze, nickel, nickel-ironalloy, and titanium.

When ceramics is used for the thin plate section 16 a, 16 b in the samemanner as the movable section 20 a, 20 b and the fixation section 22, itis preferable to use zirconia. Especially, a material containing a majorcomponent of stabilized zirconia and a material containing a majorcomponent of partially stabilized zirconia are used most preferably,because of the large mechanical strength even in the case of the thinwall thickness, the high toughness, and the small reactivity with thepiezoelectric/electrostrictive layer 26 and the electrode material.

The piezoelectric/electrostrictive element 24 a, 24 b has at least thepiezoelectric/electrostrictive layer 26 and the pair of electrodes 28,30 for applying the electric field to the piezoelectric/electrostrictivelayer 26. It is possible to use, for example,piezoelectric/electrostrictive elements of the unimorph type and thebimorph type. However, those of the unimorph type combined with the thinplate section 16 a, 16 b are suitable for thepiezoelectric/electrostrictive device 10A as described above, becausethey are excellent in stability of the generated displacement amount andthey are advantageous to realize the light weight.

For example, as shown in FIG. 1, it is possible to preferably use, forexample, the piezoelectric/electrostrictive element comprising the firstelectrode 28, the piezoelectric/electrostrictive layer 26, and thesecond electrode 30 which are stacked in the layered configuration.Additionally, it is also preferable to provide the multiple stagestructure as shown in FIGS. 5 to 9. In this arrangement, the positionaldiscrepancy of the film (electrode film) for constructing the electrode28, 30, i.e., for example, the positional discrepancy of the electrode28 in the in-plane direction on the perpendicular projection planedisposed as every other layer is not more than 50 μm. This facts alsoholds for the electrode 30.

As shown in FIG. 1, the piezoelectric/electrostrictive element 24 a, 24b is preferably formed on the outer surface side of thepiezoelectric/electrostrictive device 10A in view of the fact that thethin plate sections 16 a, 16 b can be driven to a greater extent.However, the piezoelectric/electrostrictive element 24 a, 24 b may beformed on the inner surface side of the piezoelectric/electrostrictivedevice 10A, i.e., on the inner wall surface of the hole 12 depending on,for example, the form of use. Alternatively, thepiezoelectric/electrostrictive elements 24 a, 24 b may be formed both onthe outer surface side and on the inner surface side of thepiezoelectric/electrostrictive device 10A.

Piezoelectric ceramics is preferably used for thepiezoelectric/electrostrictive layer 26. However, it is also possible touse electrostrictive ceramics, ferroelectric ceramics, oranti-ferroelectric ceramics. However, when thepiezoelectric/electrostrictive device 10A is used, for example, toposition the magnetic head of the hard disk drive, it is important toprovide the linearity concerning the displacement amount of the movablesection 20 and the driving voltage or the output voltage. Therefore, itis preferable to use a material having small strain hysteresis. It ispreferable to use a material having a coercive electric field of notmore than 10 kV/mm.

Specified materials include ceramics containing, for example, leadzirconate, lead titanate, lead magnesium niobate, lead nickel niobate,lead zinc niobate, lead manganese niobate, lead antimony stannate, leadmanganese tungstate, lead cobalt niobate, barium titanate, sodiumbismuth titanate, potassium sodium niobate, and strontium bismuthtantalate singly or in mixture.

Especially, a material containing a major component of lead zirconate,lead titanate, and lead magnesium niobate, or a material containing amajor component of sodium bismuth titanate is preferably used, in orderto obtain the product having a stable composition with a highelectromechanical coupling coefficient and a piezoelectric constant andwith small reactivity with the thin plate sections 16 a, 16 b (ceramics)when the thin plate section 16 a, 16 b is made of ceramics, and thepiezoelectric/electrostrictive layer 26 is sintered in an integratedmanner.

It is also preferable to use ceramics obtained by adding, to thematerial described above, for example, oxides of lanthanum, calcium,strontium, molybdenum, tungsten, barium, niobium, zinc, nickel,manganese, cerium, cadmium, chromium, cobalt, antimony, iron, yttrium,tantalum, lithium, bismuth, and stannum, or compounds each containing atleast one component to be finally formed into oxide, singly or inmixture.

For example, when lanthanum and/or strontium is contained in the majorcomponents of lead zirconate, lead titanate, and lead magnesium niobate,an advantage is obtained in some cases, for example, in such a way thatthe coercive electric field and the piezoelectric characteristic can beadjusted.

It is desirable to avoid the addition of a material such as silica whichtends to form glass, because of the following reason. That is, thematerial such as silica tends to react with thepiezoelectric/electrostrictive material during the heat treatment forthe piezoelectric/electrostrictive layer. As a result, the compositionis varied, and the piezoelectric characteristic is deteriorated.

On the other hand, it is preferable that thepiezoelectric/electrostrictive element 24 a, 24 b and the pair ofelectrodes 28, 30 are made of metal which is solid at room temperatureand which is excellent in conductivity. For example, it is possible touse metal simple substance or alloy of, for example, aluminum, titanium,chromium, iron, cobalt, nickel, copper, zinc, niobium, molybdenum,ruthenium, palladium, rhodium, silver, stannum, tantalum, tungsten,iridium, platinum, gold, and lead. It is also preferable to use a cermetmaterial obtained by dispersing, in the metal described above, ceramicsof the same material as that of the piezoelectric/electrostrictive layer26 or the material different from that of thepiezoelectric/electrostrictive layer 26.

The material for the electrodes 28, 30 of thepiezoelectric/electrostrictive element 24 a, 24 b is selected anddetermined depending on the method for forming thepiezoelectric/electrostrictive layer 26. For example, when thepiezoelectric/electrostrictive layer 26 is formed by sintering on thefirst electrode 28 after the first electrode 28 is formed on the thinplate section 16 a, 16 b, it is necessary for the first electrode 28 touse high melting point metal such as platinum, palladium,platinum-palladium alloy, and silver-palladium alloy which does notchange at the sintering temperature for thepiezoelectric/electrostrictive layer 26. However, the electrodeformation can be performed at a low temperature for the second electrode30 which is formed on the piezoelectric/electrostrictive layer 26 whenlocated at the outermost layer after forming thepiezoelectric/electrostrictive layer 26. Therefore, it is possible forthe second electrode 30 to use low melting point metal such as aluminum,gold, and silver.

When the stacked type piezoelectric/electrostrictive element 24 isaffixed to the thin plate section 16 a, 16 b by the aid of the adhesive202, it is preferable that the piezoelectric/electrostrictive layer 26and the electrodes 28, 30 (electrode films) are stacked and integratedinto one unit in a multilayered configuration, and then they arecollectively sintered. In this case, high melting point metal such asplatinum, palladium, and alloy thereof is used for the electrodes 28,30. It is preferable that the electrode 28, 30 is made of cermet as amixture of the high melting point metal and thepiezoelectric/electrostrictive material or another ceramics.

The thickness of the electrode 28, 30 also serves as a factor toconsiderably decrease the displacement of thepiezoelectric/electrostrictive element 24 a, 24 b. Therefore, it ispreferable, especially for the electrode formed after the sintering ofthe piezoelectric/electrostrictive layer 26, to use organic metal pastecapable of obtaining a dense and thinner film after the sintering, forexample, a material such as gold resinate paste, platinum resinatepaste, and silver resinate paste.

Next, explanation will be made with reference to FIGS. 16A to 23 forseveral methods for producing the piezoelectric/electrostrictive device10A according to the first embodiment.

In the piezoelectric/electrostrictive device 10A according to the firstembodiment, the thin plate section 16 a, 16 b is made of metal, and theconstitutive material for each of the movable section 20 and thefixation section 22 is ceramics. Therefore, it is preferable that theconstitutive elements of the piezoelectric/electrostrictive device 10Aconcerning the fixation section 22 and the movable section 20, exceptfor the thin plate sections 16 a, 16 b and thepiezoelectric/electrostrictive elements 24 a, 24 b, are produced byusing the ceramic green sheet-stacking method. On the other hand, it ispreferable that the piezoelectric/electrostrictive elements 24 a, 24 bas well as the respective terminals 32, 34 are produced by using thefilm formation method, for example, for the thin film and the thickfilm.

The thin plate sections 16 a, 16 b are preferably secured to the sidesurfaces of the movable section 20 and the fixation section 22 by theaid of the adhesive 200. The piezoelectric/electrostrictive element 24a, 24 b is preferably secured onto the thin plate section 16 a, 16 b bythe aid of the adhesive 202.

According to the ceramic green sheet-stacking method in which themovable section 20 and the fixation section 22 of thepiezoelectric/electrostrictive device 10A can be formed in an integratedmanner, the time-dependent change of state scarcely occurs at the joinedportions of the respective members. Therefore, this method provides thehigh reliability of the joined portion, and it is advantageous to ensurethe rigidity.

In the piezoelectric/electrostrictive device 10A according to the firstembodiment, the boundary portion between the thin plate section 16 a, 16b and the fixation section 22 and the boundary portion between the thinplate section 16 a, 16 b and the movable section 20 function assupporting points for expressing the displacement. Therefore, thereliability of each of the boundary portions is an important point whichdominates the characteristic of the piezoelectric/electrostrictivedevice 10A.

The production methods described below are excellent in reproducibilityand formability. Therefore, it is possible to obtain thepiezoelectric/electrostrictive device having a predetermined shapewithin a short period of time with good reproducibility.

A first production method for the piezoelectric/electrostrictive device10A according to the first embodiment will be specifically explainedbelow. The following definitions are now made. The stack, which isobtained by stacking the ceramic green sheets, is defined to be theceramic green stack 158 (see, for example, FIG. 16B). The integratedmatter, which is obtained by sintering the ceramic green stack 158, isdefined to be the ceramic stack 160 (see, for example, FIG. 17A). Thestuck or glued matter comprising the ceramic stack 160 and the metalplate is defined to be the hybrid stack 162 (see FIG. 18). Theintegrated matter comprising the movable section 20, the thin platesections 16 a, 16 b, and the fixation section 22, which is obtained bycutting off unnecessary portions from the hybrid stack 162, is definedto be the substrate 14D (see FIG. 19).

In the first production method, the hybrid stack 162 is finally cut intochip units to produce a large number of piezoelectric/electrostrictivedevices 10A. However, in order to simplify the explanation, descriptionwill be made principally for the case in which one individual ofpiezoelectric/electrostrictive device 10A is produced.

At first, for example, a binder, a solvent, a dispersing agent, and aplasticizer are added and mixed with a ceramic powder such as zirconiato prepare a slurry. The slurry is subjected to a defoaming treatment,and then a ceramic green sheet having a predetermined thickness isprepared in accordance with, for example, the reverse roll coater methodand the doctor blade method.

Subsequently, the ceramic green sheet is processed into those havingvarious shapes as shown in FIG. 16A in accordance with, for example, thepunching out based on the use of the mold and the laser machining toprepare a plurality of ceramic green sheets for forming the substrate.Specifically, a plurality (for example, four) of ceramic green sheets50A to 50D each of which is formed with a window 54 for forming at leastthe hole 12 thereafter, and a ceramic green sheet 102 which iscontinuously formed with a window 54 for forming the hole 12 thereafterand a window 100 for forming the movable section 20 having the mutuallyopposing end surfaces 36 a, 36 b are prepared.

After that, as shown in FIG. 16B, the ceramic green sheets 50A to 50D,102 are stacked and secured under pressure to form a ceramic green stack158. The stacking is performed while the ceramic green sheet 102 ispositioned at the center. After that, the ceramic green stack 158 issintered to obtain a ceramic stack 160 as shown in FIG. 17A. At thisstage, the ceramic stack 160 is formed such that the hole 130 is formedby the windows 54, 100.

Subsequently, as shown in FIG. 17B, the piezoelectric/electrostrictiveelements 24 a, 24 b, which are constructed as separate members, arerespectively glued with an epoxy adhesive 202 to the surfaces of metalplates 152A, 152B to serve as the thin plate sections.

Subsequently, the metal plates 152A, 152B are glued to the ceramic stack160 with an epoxy adhesive 200 so that the ceramic stack 160 isinterposed between the metal plates 152A, 152B and the hole 130 isclosed thereby to provide a hybrid stack 162 (see FIG. 18).

Subsequently, as shown in FIG. 18, the hybrid stack 162, which is formedwith the piezoelectric/electrostrictive elements 24 a, 24 b, is cutalong cutting lines C1, C2, C5 to thereby cut off side portions andforward end portions of the hybrid stack 162. As a result of the cutoff,as shown in FIG. 19, the piezoelectric/electrostrictive device 10Aaccording to the first embodiment is obtained, in which thepiezoelectric/electrostrictive elements 24 a, 24 b are formed on thethin plate sections constituted by the metal plates, of the substrate14D, and the movable section 20 having the mutually opposing endsurfaces 36 a, 36 b is formed.

On the other hand, in the second production method, at first, as shownin FIG. 20A, a plurality (for example, four) of ceramic green sheets 50Ato 50D each of which is formed with a window 54 for forming at least thehole 12 thereafter, and a ceramic green sheet 102 which is continuouslyformed with a window 54 for forming the hole 12 thereafter and a window100 for forming the movable section 20 having the mutually opposing endsurfaces 36 a, 36 b are prepared.

After that, as shown in FIG. 20B, the ceramic green sheets 50A to 50D,102 are stacked and secured under pressure to form a ceramic green stack158. After that, the ceramic green stack 158 is sintered to obtain aceramic stack 160 as shown in FIG. 21A. At this stage, the ceramic stack160 is formed such that the hole 130 is formed by the windows 54, 100.

Subsequently, as shown in FIG. 21B, the metal plates 152A, 152B areglued to the ceramic stack 160 with the epoxy adhesive 200 so that theceramic stack 160 is interposed between the metal plates 152A, 152B andthe hole 130 is closed thereby to provide a hybrid stack 162. In thisprocedure, when the piezoelectric/electrostrictive elements 24 a, 24 bare affixed to the surfaces of the glued metal plates 152A, 152B, thehole 130 is optionally filled with a filler material 164 as shown inFIG. 21A so that a sufficient gluing pressure may be applied.

It is necessary to finally remove the filler material 164. Therefore, itis preferable to use a hard material which is easily dissolved in asolvent or the like. The material includes, for example, organic resin,wax, and brazing filler material. It is also possible to adopt amaterial obtained by mixing ceramic powder as a filler with organicresin such as acrylic.

Subsequently, as shown in FIG. 21B, the piezoelectric/electrostrictiveelements 24 a, 24 b, which are constructed as separate members, areglued with the epoxy adhesive 202 to the surfaces of the metal plates152A, 152B of the hybrid stack 162. The separate members of thepiezoelectric/electrostrictive elements 24 a, 24 b can be formed, forexample, in accordance with the ceramic green sheet-stacking method.

Subsequently, as shown in FIG. 22, the hybrid stack 162, which is formedwith the piezoelectric/electrostrictive elements 24 a, 24 b, is cutalong cutting lines C1, C2, C5 to thereby cut off side portions andforward end portions of the hybrid stack 162. As a result of the cutoff,as shown in FIG. 23, the piezoelectric/electrostrictive device 10Aaccording to the first embodiment is obtained, in which thepiezoelectric/electrostrictive elements 24 a, 24 b are formed on thethin plate sections constituted by the metal plates, of the substrate14D, and the movable section 20 having the mutually opposing endsurfaces 36 a, 36 b is formed.

When all of the substrate section is made of metal, for example, theportions corresponding to the ceramic stack 160 shown in FIG. 17A areformed by means of molding. Further, bulk-shaped members may be formedin accordance with the method of grinding machining, wire electricdischarge machining, mold stamping, or chemical etching, or thin metalmaterials may be stacked to form the substrate section in accordancewith the cladding method.

Next, a piezoelectric/electrostrictive device 10B according to thesecond embodiment will be explained with reference to FIGS. 24 to 52.

As shown in FIG. 24, the piezoelectric/electrostrictive device 10Baccording to the second embodiment comprises a pair of mutually opposingthin plate sections 16 a, 16 b, and a fixation section 22 for supportingthe thin plate sections 16 a, 16 b. A stacked typepiezoelectric/electrostrictive element 24 is arranged on one thin platesection 16 a of the pair of thin plate sections 16 a, 16 b. In FIGS. 24and 25, the stacked type piezoelectric/electrostrictive element 24 isillustrated in a simplified manner, because its structure iscomplicated. Details are shown in magnified views of FIGS. 26 to 29.

The fixation section 22 is secured, for example, by the aid of anadhesive 200 between the respective rearward ends of the pair of thinplate sections 16 a, 16 b. The forward ends of the pair of thin platesections 16 a, 16 b are open ends.

As shown in FIG. 25, for example, the movable section 20 or variousparts and members are secured, for example, by the aid of the adhesive200 between the respective forward ends of the pair of thin platesections 16 a, 16 b. The example shown in FIG. 25 is illustrative of thecase in which the movable section 20, which is constructed by the samemember as that of the fixation section 22, is secured by the aid of theadhesive 200 between the respective forward ends of the pair of thinplate sections 16 a, 16 b.

Each of the pair of thin plate sections 16 a, 16 b is made of metal. Thefixation section 22 and the movable section 20 are made of ceramics ormetal. Especially, in the examples shown in FIGS. 24 and 25, thethickness of the first thin plate section 16 a on which the stacked typepiezoelectric/electrostrictive element 24 is formed, of the pair of thinplate sections 16 a, 16 b is larger than the thickness of the secondthin plate section 16 b.

The stacked type piezoelectric/electrostrictive element 24 is affixed tothe thin plate section 16 b by the aid of an adhesive 202 such asorganic resin, glass, brazing, soldering, and eutectic bonding. That is,the stacked type piezoelectric/electrostrictive element 24 is secured bythe adhesive 202 to the thin plate section 16 a made of metal to therebyconstruct an actuator section 204 which is the driving source of thepiezoelectric/electrostrictive device 10B.

In the piezoelectric/electrostrictive device 10B, the forward end(portion to which the movable section 20 is attached) of the thin platesection 16 a (16 a and 16 b in the example shown in FIG. 25) isdisplaced in accordance with the driving of the actuator section 204.Alternatively, the displacement of the forward end of the thin platesection 16 a is electrically detected by the aid of the actuator section(transducer section in the case of the use as a sensor) 204. In thiscase, the device is utilized as a sensor.

As shown in FIG. 26, for example, the stacked typepiezoelectric/electrostrictive element 24 is constructed as follows.That is, each of the piezoelectric/electrostrictive layer 26 and thepair of electrodes 28, 30 has the multilayered structure, and the firstelectrodes 28 and the second electrodes 30 are alternately stackedrespectively to give the multiple stage structure at the portion atwhich the first electrodes 28 and the second electrodes 30 areoverlapped with each other with the piezoelectric/electrostrictive layer26 intervening therebetween.

In FIG. 26, each of the piezoelectric/electrostrictive layer 26 and thepair of electrodes 28, 30 has the multilayered structure. The firstelectrode 28 and the second electrode 30 are alternately stacked witheach other to give the substantially comb-shaped configuration. Themultiple stage structure is formed at the portion at which the firstelectrode 28 and the second electrode 30 are overlapped with each otherwith the piezoelectric/electrostrictive layer 26 interposedtherebetween.

Specifically, the stacked type piezoelectric/electrostrictive element 24has the approximately rectangular parallelepiped-shaped configuration,comprising a plurality of piezoelectric/electrostrictive layers 26 and aplurality of electrode films 28, 30. The electrode films 28, 30, whichcontact with the upper and lower surfaces of each of thepiezoelectric/electrostrictive layers 26, are alternately led toopposite end surfaces 208, 209 respectively. End surface electrodes 28c, 30 c, which electrically connect the respective electrode films 28,30 alternately led to the opposite end surfaces 208, 209, areelectrically connected to terminals 28 b, 30 b which are formed on thesurface of the outermost layer of the piezoelectric/electrostrictivelayer 26 and which are arranged while being separated from each other bya predetermined distance Dk.

It is preferable that the predetermined distance Dk between theterminals 28 b, 30 b is not less than 20 μm. Further, the material ofthe electrode films 28, 30 to make contact with the upper and lowersurfaces of the piezoelectric/electrostrictive layer may be differentfrom the material of the end surface electrodes 28 c, 30 c. Further, atleast one of the terminals (terminal 28 b in the example shown in FIG.26) and the end surface electrode 28 c corresponding to the terminal 28b may be electrically connected with a thin film electrode film (outersurface electrode) 28 d which is thinner than the terminal 28 b and theend surface electrode 28 c.

The surface electrode film 28 d, the end surface electrodes 28 c, 30 c,and the terminals 28 b, 30 b, which are formed before sintering thepiezoelectric/electrostrictive layer 26, may be thin, and they may havelow heat resistance, as compared with the electrode layers 28, 30 whichare formed before sintering the piezoelectric/electrostrictive layer 26or which are sintered simultaneously.

FIG. 26 is illustrative of the following case. That is, thepiezoelectric/electrostrictive layer 26 has the five-layered structure.The first electrodes 28 are formed in the comb-shaped configuration sothat they are disposed on the upper surface of the first layer, theupper surface of the third layer, and the upper surface of the fifthlayer. The second electrodes 30 are formed in the comb-shapedconfiguration so that they are disposed on the upper surface of thesecond layer and the upper surface of the fourth layer.

FIG. 28 is illustrative of the following case. That is, thepiezoelectric/electrostrictive layer 26 has the five-layered structureas well. The first electrodes 28 are formed in the comb-shapedconfiguration so that they are disposed on the upper surface of thefirst layer, the upper surface of the third layer, and the upper surfaceof the fifth layer. The second electrodes 30 are formed in thecomb-shaped configuration so that they are disposed on the lower surfaceof the first layer, the upper surface of the second layer, and the uppersurface of the fourth layer.

In the case of the structures described above, it is possible tosuppress the increase in number of terminals by connecting the mutualfirst electrodes 28 and the mutual second electrodes 30 with each otherto be common. Therefore, it is possible to suppress the increase insize, which would be otherwise caused when the stacked typepiezoelectric/electrostrictive element 24 is used.

As described above, the driving force of the actuator section 204 isincreased by using the stacked type piezoelectric/electrostrictiveelement 24, and thus it is possible to obtain the large displacement.Further, it is possible to realize the high resonance frequency byincreasing the rigidity of the piezoelectric/electrostrictive device 10Bitself. Thus, it is easy to achieve the high speed of the displacementaction.

When the number of stages is increased, it is possible to increase thedriving force of the actuator section 204. However, the electric powerconsumption is also increased in accordance therewith. Therefore, whenthe present invention is carried out, the number of stages may beappropriately determined depending on the way of use and the state ofuse. In the case of the piezoelectric/electrostrictive device 10Baccording to the second embodiment, the width of the thin plate section16 a, 16 b (distance in the Y axis direction) is basically unchanged,even when the driving force of the actuator section 204 is increased,owing to the use of the stacked type piezoelectric/electrostrictiveelement 24. Therefore, the device is extremely preferred to makeapplication, for example, to the actuator for the purpose of the ringingcontrol and the positioning of the magnetic head for the hard disk to beused in an extremely narrow gap.

The stacked type piezoelectric/electrostrictive element 24 is preferablyformed at the following position with respect to the thin plate section16 a. That is, the forward end 208 of the multilayered member forconstructing the stacked type piezoelectric/electrostrictive element 24is disposed at the position not including at least the fixation section22 as viewed in plan view (position included in the hole 12 formedbetween the movable section 20 and the fixation section 22 in theexample shown in FIG. 25). The rearward end 209 of the multilayeredmember for constructing the stacked type piezoelectric/electrostrictiveelement 24 is disposed at the position including at least the fixationsection 22 as viewed in plan view. The end 28 a of the electrode 28 isformed at the position including at least the fixation section 22 asviewed in plan view, and the end 30 a of the electrode 30 is formed atthe position not including at least the fixation section 22 as viewed inplan view (position included in the hole 12 formed between the movablesection 20 and the fixation section 22 as well in the example shown inFIG. 25).

The voltage is applied to the pair of electrodes 28, 30 via ends(hereinafter referred to as “terminals 28 b, 30 b”) of the respectiveelectrodes 28, 30 formed on the fifth layer of thepiezoelectric/electrostrictive layer 30. The respective terminals 28 b,30 b are formed to be separated from each other in such a degree thatthey can be electrically insulated from each other.

The spacing distance Dk between the terminals 28 b, 30 b is preferablynot less than 20 μm, and it is preferably not less than 50 μm when thethickness of the terminal 28 b, 30 b is 1 μm to 30 μm. The terminals 28b, 30 b may be made of the same material as that of the internalelectrodes 28, 30, or they may be made of a material differenttherefrom. For example, the same material may be used when the terminals28 b, 30 b are sintered simultaneously with thepiezoelectric/electrostrictive layer 26. The different materials may beused when the sintering is performed separately.

It is preferable for the end surface electrodes 28 c, 30 c that theinternal electrodes 28, 30 and the piezoelectric/electrostrictive layer26 are sintered, and then their end surfaces are subjected to, forexample, grinding and polishing to effect the electric connectionbetween the internal electrodes and the end surface electrodes. Thematerial of the end surface electrodes 28 c, 30 c may be the same as, ordifferent from that of the internal electrodes 28, 30. For example, itis preferable that platinum paste is utilized for the internalelectrodes 28, 30, gold resinate is utilized for the outer surfaceelectrode 28 d, and gold paste is utilized for the end surfaceelectrodes 28 c, 30 c and the terminals 28 b, 30 b. However, it is alsopossible to adopt approximately the same construction as that of thepiezoelectric/electrostrictive device according to the first embodimentdescribed above.

In this arrangement, the piezoelectric/electrostrictive device 10B canbe independently fixed by utilizing the surface other than the surfaceon which the terminals 28 b, 30 b are arranged. As a result, it ispossible to obtain high reliability for both of the fixation of thepiezoelectric/electrostrictive device 10B and the electric connectionbetween the circuit and the terminals 28 b, 30 b. In this arrangement,the electric connection between the terminals 28 b, 30 b and the circuitis made, for example, by means of the flexible printed circuit, theflexible flat cable, and the wire bonding.

As described above, in the piezoelectric/electrostrictive device 10Baccording to the second embodiment, the actuator section 204 isconstructed by securing the stacked type piezoelectric/electrostrictiveelement 24 onto the thin plate section 16 a made of metal by the aid ofthe adhesive 202. Therefore, it is possible to greatly displace the thinplate section 16 a (and 16 b) even when the areal size of the stackedtype piezoelectric/electrostrictive element 24 is not widened as viewedin plan view. Further, the thin plate section 16 a (and 16 b) is made ofmetal. Therefore, the device is excellent in strength and toughness, andit is possible to respond to the quick displacement action as well.

In other words, in the second embodiment, it is possible to sufficientlyrespond to the variation of environment of use and the severe state ofuse. The device is excellent in shock resistance. It is possible torealize the long life time of the piezoelectric/electrostrictive device10B, and it is possible to improve the handling performance of thepiezoelectric/electrostrictive device 10B. Further, the thin platesection can be greatly displaced at a relatively low voltage. Therigidity of the thin plate section 16 a (and 16 b) is high, the filmthickness of the actuator section 204 is thick, and the rigidity of theactuator section 204 is high. Accordingly, it is possible to achieve therealization of the high speed (realization of the high resonancefrequency) of the displacement action of the thin plate section 16 a(and 16 b).

Usually, in order to drive, at a high speed, the actuator section 204constructed by combining the thin plate section 16 a and thepiezoelectric/electrostrictive element 24 which makes straindeformation, it is necessary to increase the rigidity of the actuatorsection 204. In order to obtain large displacement, it is necessary todecrease the rigidity of the actuator section 204.

However, in the piezoelectric/electrostrictive device 10B according tothe second embodiment, the thin plate sections 16 a, 16 b, whichconstitute the actuator section 204, are opposed to one another toprovide the pair of thin plate sections 16 a, 16 b. The fixation section22 is secured by the adhesive 200 between the respective rearward endsof the pair of thin plate sections 16 a, 16 b to construct the multiplestage structure of the piezoelectric/electrostrictive element 24. Theposition of the piezoelectric/electrostrictive element 24, the materialand the size of the constitutive members are appropriately selected toconstruct the piezoelectric/electrostrictive device 10B. Therefore, itis possible to effect the both of the contradicting characteristicsdescribed above. When the object, which has the substantially the samedegree of size as that of the fixation section 22, intervenes betweenthe open ends of the pair of thin plate sections 16 a, 16 b, the minimumresonance frequency of the structure is not less than 20 kHz. Further,the relative displacement amount concerning the object and the fixationsection 22 can be not less than 0.5 μm at a substantial applied voltageof 30 V at a frequency which is not more than ¼ of the resonancefrequency.

As a result, it is possible to greatly displace the pair of thin platesections 16 a, 16 b. Further, it is possible to achieve the realizationof the high speed (realization of the high resonance frequency) of thedisplacement action of the piezoelectric/electrostrictive device 10B,especially of the pair of thin plate sections 16 a, 16 b.

In the piezoelectric/electrostrictive device 10B according to the secondembodiment, the minute displacement of thepiezoelectric/electrostrictive element 24 is amplified into the largedisplacement action by utilizing the bending of the thin plate sections16 a, 16 b, and it is transmitted to the movable section 20. Therefore,the movable section 20 can be greatly displaced with respect to themajor axis m (see FIG. 14) of the piezoelectric/electrostrictive device10B.

In the piezoelectric/electrostrictive device 10B according to the secondembodiment, it is unnecessary that all of the parts are formed with thepiezoelectric/electrostrictive material which is a fragile materialhaving a relatively heavy weight. Therefore, the device has thefollowing advantages. That is, the device has the high mechanicalstrength, and it is excellent in handling performance, shock resistance,and moisture resistance. Further, the operation of the device isscarcely affected by harmful vibration (for example, noise vibration andremaining vibration during high speed operation).

Further, as shown in FIG. 24, the forward ends of the pair of thin platesections 16 a, 16 b are the open ends. Accordingly, when various membersor parts are attached to the piezoelectric/electrostrictive device 10B,it is possible to utilize the forward ends of the pair of thin platesections 16 a, 16 b. The member or the part can be attached in such away that the member or the part is interposed by the forward ends. Inthis case, it is possible to provide a large attachment area for themember or the part, and it is possible to improve the attachmentperformance for the part. Further, the member or the part to be attachedis consequently included in the pair of thin plate sections 16 a, 16 b.Therefore, it is possible to decrease the size of thepiezoelectric/electrostrictive device in the Y direction after attachingthe member or the part. Thus, the device is advantageous to realize thecompact size.

Of course, as shown in FIG. 25, when the movable section 20 is securedbetween the respective forward ends of the pair of thin plate sections16 a, 16 b, then various members or parts are secured, for example, bythe aid of an adhesive to the first principal surface of the movablesection 20.

In the second embodiment, the forward end 208 of the multilayered memberfor constructing the stacked type piezoelectric/electrostrictive element24 is disposed at the position not including at least the fixationsection 22 as viewed in plan view. The rearward end of the multilayeredmember is disposed at the position including at least the fixationsection 22 as viewed in plan view. The end 28 a of the electrode 28 isdisposed at the position including at least the fixation section 22 asviewed in plan view. The end 30 a of the electrode 30 is disposed at theposition not including the fixation section 22 as viewed in plan view.

For example, if the respective ends of the pair of electrodes 28, 30 areformed at the position included in the movable section 20, then it isfeared that the displacement action of the pair of thin plate sections16 a, 16 b is restricted by the stacked typepiezoelectric/electrostrictive element 24, and it is impossible toobtain the large displacement. However, in the second embodiment, theforegoing positional relationship is adopted. Therefore, it is possibleto avoid the inconvenience of the restriction of the displacement actionof the movable section 20, and it is possible to increase thedisplacement amount of the pair of thin plate sections 16 a, 16 b.

Next, explanation will be made for preferred illustrative constructionsof the piezoelectric/electrostrictive device 10B according to the secondembodiment. The preferred illustrative constructions are approximatelythe same as those of the piezoelectric/electrostrictive device accordingto the first embodiment described above. Therefore, explanation will bemade for only the preferred illustrative constructions inherent in thepiezoelectric/electrostrictive device 10B according to the secondembodiment.

At first, in the piezoelectric/electrostrictive device 10B according tothe second embodiment, the shape of the device 10B is not theplate-shaped configuration like the conventional one. When the movablesection 20 is provided, the movable section 20 and the fixation section22 form the rectangular parallelepiped-shaped configuration. The pair ofthin plate sections 16 a, 16 b are provided so that the side surfaces ofthe movable section 20 and the fixation section 22 are continuous togive the rectangular annular configuration. Therefore, it is possible toselectively enhance the rigidity of the piezoelectric/electrostrictivedevice 10B in the Y axis direction.

That is, in the piezoelectric/electrostrictive device 10B, it ispossible to selectively generate only the action of the movable section20 in the plane (in the XZ plane). It is possible to suppress the actionof the pair of thin plate sections in the YZ plane (action in theso-called swaying direction).

It is desirable that the thin plate sections 16 a, 16 b are made ofmetal. The fixation section 22 and the movable section 20 may be made ofmaterials of different types, but they are more preferably made ofmetal. For example, organic resin, brazing material, or solder may beused to glue the thin plate sections 16 a, 16 b to the fixation section22 and glue the thin plate sections 16 a, 16 b to the movable section20. However, it is more preferable to form an integrated structureformed by diffusion joining or welding between metal materials. It ismore desirable to use metal subjected to the cold rolling process,because of the high strength owing to the presence of a great degree ofdislocation.

In the second embodiment, the stacked typepiezoelectric/electrostrictive element 24 is formed on only one thinplate section 16 a. Therefore, the device can be produced inexpensivelyas compared with a device (modified embodiment) in which the stackedtype piezoelectric/electrostrictive elements 24 a, 24 b are formed onthe pair of thin plate sections 16 a, 16 b respectively as shown in FIG.30. Further, in the second embodiment, when the observation is made in astate in which the movable section 20 is secured, then the thin platesection 16 a having the large thickness, on which the stacked typepiezoelectric/electrostrictive element 24 is formed, is directlydisplaced, and the thin plate section 16 b having the thin thickness, onwhich the stacked type piezoelectric/electrostrictive element 24 is notformed, is displaced in cooperation therewith. Accordingly, it ispossible to cause the displacement to a greater extent.

The formation of the stacked type piezoelectric/electrostrictive element24 on the thin plate section 16 a can be realized by gluing the stackedtype piezoelectric/electrostrictive element 24 to the thin plate section16 a, for example, with organic resin, brazing material, or solder. Whenthe element is glued at a low temperature, it is desirable to useorganic resin. When the element is allowed to be glued at a hightemperature, it is preferable to use, for example, brazing material,solder, and glass. However, the coefficient of thermal expansion isgenerally differs among the thin plate section 16 a, the stacked typepiezoelectric/electrostrictive element 24, and the adhesive 202.Therefore, it is desirable that the gluing temperature is low in ordernot to generate any stress in the stacked typepiezoelectric/electrostrictive element 24 due to the difference incoefficient of thermal expansion. In the case of organic resin, thegluing can be generally effected at a temperature of not more than 180°C. Therefore, organic resin is preferably adopted. More preferably, itis desirable to use a room temperature setting adhesive. When thefixation of the thin plate section 16 a, 16 b and thepiezoelectric/electrostrictive element 24 is performed simultaneouslywith, or after the fixation of the movable section 20, the fixationsection 22 and the thin plate section 16 a, 16 b, if the fixationsection 22 or the movable section 20 has the open type structure, thenit is possible to effectively reduce the strain which would be otherwisecaused between the different types of materials.

In order not to exert any thermal stress on the stacked typepiezoelectric/electrostrictive element 24, it is preferable that thestacked type piezoelectric/electrostrictive element 24 is glued to thethin plate section 16 a with organic resin, and the fixation isperformed in separate steps for the thin plate sections 16 a, 16 b, thefixation section 22, and the movable section 20.

As shown in FIG. 31, when the part of the piezoelectric/electrostrictiveelement 24 is located at the fixation section 22, it is preferable that(1−Lb/La) is not less than 0.4, and more preferably 0.5 to 0.8 providedthat La represents a shortest distance concerning the pair of thin platesections 16 a, 16 b between a boundary portion with respect to themovable section 20 and a boundary portion with respect to the fixationsection 22, and Lb represents a shortest distance of distances from theboundary portion between the thin plate section 16 a and the movablesection 20 to any one of the ends 28 a, 30 a of the pair of electrodes28, 30 of the stacked type piezoelectric/electrostrictive element 24. If(1−b/La) is not more than 0.4, it is impossible to make largedisplacement. When (1−Lb/La) is 0.5 to 0.8, it is easy to successivelyachieve both of the displacement and the resonance frequency. However,in this case, it is more appropriate to use a structure in which thestacked type piezoelectric/electrostrictive element 24 is formed on onlyone thin plate section 16 a. This fact also holds when the part of thepiezoelectric/electrostrictive element 24 is located at the movablesection 20.

It is preferable that the total thickness of the stacked typepiezoelectric/electrostrictive element 24 is not less than 40 μm. If thetotal thickness is less than 40 μm, it is difficult to glue the stackedtype piezoelectric/electrostrictive element 24 to the thin plate section16 a. It is desirable that the total thickness is not more than 180 μm.If the total thickness exceeds 180 μm, it is difficult to realize acompact size of the piezoelectric/electrostrictive device 10B.

As for the portion of the stacked type piezoelectric/electrostrictiveelement 24 to make contact with the thin plate section 16 a, when themetal such as brazing material and solder layer is used as the adhesive202, it is preferable that the electrode layer exists at the lowermostlayer in view of the wettability as shown in FIGS. 28 and 29. FIGS. 28and 29 show the state in which the electrode film for constructing thesecond electrode 30 is arranged.

When the stacked type piezoelectric/electrostrictive element 24 as shownin FIG. 26 and FIG. 28 is glued to the thin plate section 16 a by theaid of the metal layer such as the brazing material and the solderlayer, it is preferable to chamfer the angular portion at which at leastone electrode 28 exists, of the lower surface of the stacked typepiezoelectric/electrostrictive element 24 as shown in FIG. 27 and FIG.29, because of the following reason. That is, it is intended to preventthe pair of electrodes 28, 30 from formation of short circuit whichwould be otherwise formed via the metal layer and the thin plate section16 a. FIG. 27 is illustrative of a case in which two angular portions,at which the pair of electrodes 28, 30 exist, are chamfered. FIG. 29 isillustrative of a case in which an angular portion, at which the firstelectrode 28 exists, is chamfered.

Those preferably used as the adhesive 202 for gluing the stacked typepiezoelectric/electrostrictive element 24 to the thin plate section 16 aand the adhesive 200 for gluing the thin plate sections 16 a, 16 b, forexample, to the fixation section 22 include two-part type reactiveadhesives such as those based on epoxy and isocyanate, instantaneousadhesives such as those based on cyanoacrylate, and hot melt adhesivessuch as those based on ethylene-vinyl acetate copolymer. Especially, itis preferable to use those having Shore D hardness of not less than 80as the adhesive 202 for gluing the stacked typepiezoelectric/electrostrictive element 24 to the thin plate section 16a.

It is desirable that an organic adhesive containing a filler such asmetal and ceramics is used as the adhesive 202 for gluing the thin platesection 16 a, 16 b and the piezoelectric/electrostrictive element 24 (24a, 24 b). In this case, it is desirable that the thickness of theadhesive 202 is not more than 100 μm, because of the following reason.That is, when the filler is contained, then the substantial thickness ofthe resin component is decreased, and it is possible to maintain a highhardness of the adhesive.

It is also preferable to use inorganic adhesives as the adhesive 200,202, other than the organic adhesives described above. The inorganicadhesive includes, for example, glass, cement, solder, and brazingmaterial.

On the other hand, as for the shape and the material quality for thethin plate sections 16 a, 16 b, it is enough to have the flexibility,with the mechanical strength of such a degree that no breakage is causeddue to bending deformation. Metal is preferably adopted. In this case,as described above, it is preferable to use a metal material which hasthe flexibility and which is capable of the bending displacement.Specifically, it is preferable to use a metal material which has aYoung's modulus of not less than 100 GPa.

Preferably, it is desirable that the thin plate section 16 a, 16 b ismade of an iron-based material such as various spring steel materials,marageing stainless steel materials, and stainless steel materialsincluding, for example, austenite-based stainless steel materials suchas SUS301, SUS304, AISI653, and SUH660, ferrite-based stainless steelmaterials such as SUS430 and SUS434, maltensite-based stainless steelmaterials such as SUS410 and SUS630, and semiaustenite-based stainlesssteel materials such as SUS631 and AISI632. Alternatively, it isdesirable that the thin plate section 16 a, 16 b is made of anon-ferrous material such as superelastic titanium alloy represented bytitanium-nickel alloy, brass, cupronickel, aluminum, tungsten,molybdenum, beryllium copper, phosphor bronze, nickel, nickel-ironalloy, and titanium.

Next, explanation will be made with reference to FIGS. 32 to 40 forseveral production methods for manufacturing thepiezoelectric/electrostrictive device 10B according to the secondembodiment.

In the third production method, as shown in FIG. 32, a rectangular hole252 having a size of width: 1 mm×length: 8 mm is firstly bored through acentral portion of a stainless steel plate 250 having a size of width:1.6 mm×length: 10 mm×thickness: 0.9 mm to manufacture a substrate 258having a rectangular annular structure with support sections 254, 256arranged on both sides of the hole 252 respectively.

After that, as shown in FIG. 33, a first stainless steel thin plate 260having a size of width: 1.6 mm×length: 10 mm×thickness: 0.05 and asecond stainless steel thin plate 262 having a size of width: 1.6mm×length: 10 mm×thickness: 0.02 (see FIG. 35) are prepared.

After that, as shown in FIG. 33, the adhesive 202 (for example, anadhesive made of epoxy resin) is formed by the screen printing on aportion of the upper surface of the first stainless steel thin plate 260on which the stacked type piezoelectric/electrostrictive element 24 isformed. After that, as shown in FIG. 34, the stacked typepiezoelectric/electrostrictive element 24 is glued to the firststainless steel thin plate 260 by the aid of the adhesive 202.

After that, as shown in FIG. 35, the adhesive 200 (for example, anadhesive made of epoxy resin) is formed by the screen printing on therespective support sections 254, 256 of the substrate 258.

After that, the first stainless steel thin plate 260, on which thestacked type piezoelectric/electrostrictive element 24 has been alreadyformed, is glued to the first surface of each of the support sections254, 256 by the aid of the adhesive 200. The second stainless steel thinplate 262 is glued to the second surface of each of the support sections254, 256 by the aid of the adhesive 200. Further, the pressure isapplied to the first and second stainless steel thin plates 260, 262 ina direction to interpose the substrate 258 to manufacture a masterdevice block 270 shown in FIG. 36. The applied pressure is 0.1 to 10kgf/cm².

After that, as shown in FIG. 36, the master device block 270 is cut intoportions along cutting lines 272 to divide the block into the individualpiezoelectric/electrostrictive devices 10B as shown in FIG. 25. Thecutting process was performed by using a wire saw having a wire diameterof 0.1 mm and a spacing distance of 0.2 mm. When the wire saw is used,it is possible to prescribe substantially the same size for the width ofthe piezoelectric/electrostrictive element 24, the width of the thinplate section 16 a, and the width of the adhesives 200, 202, althoughthese components are made of different materials respectively.

Next, in the fourth production method, as shown in FIG. 37, arectangular hole 252 having a size of width: 1 mm×length: 8 mm is boredthrough a central portion of a stainless steel plate 250 having a sizeof width: 1.6 mm×length: 10 mm×thickness: 0.9 mm to manufacture asubstrate 258 having a rectangular annular structure with supportsections 254, 256 arranged on both sides of the hole 252 respectively.

After that, the adhesive 200 (for example, an adhesive made of epoxyresin) is formed by the screen printing on the respective supportsections 254, 256 of the substrate 258.

After that, as shown in FIG. 38, a first stainless steel thin plate 260having a size of width: 1.6 mm×length: 10 mm×thickness: 0.05 is glued tothe first surface of each of the support sections 254, 256 by the aid ofthe adhesive 200. A second stainless steel thin plate 262 having a sizeof width: 1.6 mm×length: 10 mm×thickness: 0.02 is glued to the secondsurface of each of the support sections 254, 256 by the aid of theadhesive 200. Further, the pressure is applied to the first and secondstainless steel thin plates 260, 262 in a direction to interpose thesubstrate 258. The applied pressure is 0.1 to 10 kgf/cm².

After that, the adhesive 202 (for example, an adhesive made of epoxyresin) is formed by the screen printing on a portion of the uppersurface of the first stainless steel thin plate 260 on which the stackedtype piezoelectric/electrostrictive element 24 is formed.

After that, as shown in FIG. 40, the stacked typepiezoelectric/electrostrictive element 24 is glued to the firststainless steel thin plate 260 by the aid of the adhesive 202 tomanufacture a master device block 270.

After that, as shown in FIG. 36, the master device block 270 is cut intoportions along cutting lines 272 to divide the block into the individualpiezoelectric/electrostrictive devices 10B as shown in FIG. 25.

A part (for example, the fixation section 22) of thepiezoelectric/electrostrictive device 10B produced in accordance withthe first and second production methods was fixed. A bias voltage of 15V and a sine wave voltage of ±15 V were applied between the pair ofelectrodes 28, 30 of the stacked type piezoelectric/electrostrictiveelement 24 to measure the displacement of the movable section 20. As aresult, the displacement was ±1.2 μm. The frequency was swept with asine wave voltage of ±0.5 V to measure the minimum resonance frequencyto exhibit the maximum displacement. As a result, the minimum resonancefrequency was 50 kHz.

In the third and fourth production methods described above, thesubstrate 258 is constructed to have the rectangular annular structurehaving the support section 254 to be formed into the movable section 20thereafter and the support section 256 to be formed into the fixationsection 22 thereafter. Alternatively, as shown in FIG. 41, a rectangularannular structure is also available, in which a hole 252 is widened tohave a frame-shaped section 254 a for supporting first and secondstainless steel thin plates 260, 262 (section for substantially definingthe thickness of a portion to allow at least the movable section 20 tointervene thereafter) and a support section 256 to be formed into thefixation section 22 thereafter.

In this case, the substrate 258 is secured by the aid of the adhesive200 so that the substrate 258 is interposed between the first and secondstainless steel thin plates 260, 262 to manufacture a master deviceblock 270 similar to one shown in FIG. 36, followed by being cut alongcutting lines 272 as shown in FIG. 36. Accordingly, as shown in FIG. 44,for example, it is possible to produce a piezoelectric/electrostrictivedevice in which the movable section 20 does not exist between theforward ends of the thin plate sections 16 a, 16 b.

Next, explanation will be made with reference to FIGS. 42 to 46 for afifth production method which is different from the third and fourthproduction methods described above.

The fifth production method is also applicable to a case in whichsupport sections 254, 256 are glued to a first stainless steel thinplate 260 and a second stainless steel thin plate 262 to manufacture amaster device block 270 in the same manner as in the third and fourthproduction methods described above, followed by being divided intoindividual piezoelectric/electrostrictive devices. The fifth productionmethod is also applicable to a case in which thepiezoelectric/electrostrictive device 10B is produced by securing thefixation section 22 (and the movable section 20, if desirable) preparedseparately to a unit prepared separately as each actuator section 204comprising the stacked type piezoelectric/electrostrictive element 24 a,24 b formed on the thin plate sections 16 a, 16 b.

In the following description, the support section 254 to be formed intothe movable section 20 thereafter and the movable section 20 areconveniently referred to as “movable section 20”, the support section256 to be formed into the fixation section 22 thereafter and thefixation section 22 are conveniently referred to as “fixation section22”, and the first and second stainless steel thin plates 260, 262 to beformed into the thin plate sections 16 a, 16 b thereafter and the thinplate sections 16 a, 16 b are conveniently referred to as “thin platesections 16 a, 16 b”.

As shown in FIG. 42, when the thin plate sections 16 a, 16 b are gluedby the aid of adhesive 200 to the movable section 20 and the fixationsection 22 respectively, if the adhesive having fluidity is used, thenit is preferable to provide bumps 280 am, 280 an, 280 bm, 280 bn for therespective thin plate sections 16 a, 16 b in order to define the placesfor forming the adhesive 200. Of course, when the adhesive having highviscosity is used, it is unnecessary to provide such a bump. The bumps280 am, 280 an, 280 bm, 280 bn may be also formed by stackingplate-shaped members.

FIG. 43 is illustrative of a case in which the adhesive having highfluidity is used as the adhesive 200 for gluing the movable section 20and the respective thin plate sections 16 a, 16 b, and the adhesivehaving high viscosity is used as the adhesive 200 for gluing thefixation section 22 and the respective thin plate sections 16 a, 16 b,wherein the bumps 280 an, 280 bn are provided at portions of the thinplate sections 16 a, 16 b for which the adhesive having high fluidity isused.

FIG. 44 is illustrative of a case in which the adhesive having highviscosity is used as the adhesive 200 for gluing the fixation section22, and the thin plate sections 16 a, 16 b, depicting a structure inwhich the bump 280 am, 280 an, 280 bm, 280 bn as described above is notprovided.

FIG. 45 is illustrative of a case in which the adhesive having highfluidity is commonly used as the adhesive 200 for gluing the fixationsection 22, the movable section 20, and the thin plate sections 16 a, 16b, especially depicting an example which is provided with projections282 am, 282 an, 282 bm, 282 bn for comparting regions for forming theadhesive 200 on the thin plate sections 16 a, 16 b.

As shown in FIG. 46 concerning the example shown in FIG. 42, it is alsopreferable that each of the size of the fixation section 22 and themovable section 20, especially the areal size of the surface opposed tothe bump 280 am, 280 bm of each of the thin plate sections 16 a, 16 bconcerning the fixation section 22 is made to be larger than the arealsize of the bump 280 am, 280 bm. Also, the areal size of a surfaceopposed to the bump 280 an, 280 bn of each of the thin plate sections 16a, 16 b concerning the movable section 20 is made to be larger than theareal size of the bump 280 an, 280 bn. Accordingly, the substantialdriving portion (portion between the bumps 280 am and 280 an and portionbetween the bumps 280 bm and 280 bn) of the thin plate sections 160 a,160 b can be defined by the bump 280 am, 280 an, 280 bm, 280 bn. Asshown in FIG. 42, when the areal size of the surface opposed to the bump280 am, 280 bm of each of the thin plate sections 16 a, 16 b concerningthe fixation section 22 is made to be substantially the same as theareal size of the bump 280 am, 280 bm, and the areal size of the surfaceopposed to the bump 280 an, 280 bn of each of the thin plate sections 16a, 16 b concerning the movable section 20 is made to be substantiallythe same as the areal size of the bump 280 an, 280 bn, it is feared thatthe dispersion in size concerning the fixation section 22 and the bump280 am, 280 bm, and the dispersion in size concerning the movablesection 20 and the bump 280 an, 280 bn affect the length of thesubstantial driving portion. FIG. 46 is illustrative of the case inwhich the size of the fixation section 22 is increased toward themovable section 20. Alternatively, it is also preferable that the sizeof the fixation section 22 is increased outwardly oppositely to thedirection toward the movable section 20. Similar structural variationsare available with regard to the movable section 20.

In FIGS. 42 to 46, the bumps 280 am, 280 bm, 280 an, 280 bn or theprojections 282 am, 282 bm, 282 an, 282 bn and the thin plate sections16 a, 16 b are integrated with the thin plate sections. However, thesecomponents may be provided by stacking appropriately processed plates bythe aid of an adhesive, in the same manner as in FIG. 19 or FIG. 23. Inthe case of the provision by means of the integration, the bumps 280 am,280 bm, 280 an, 280 bn or the projections 282 am, 282 bm, 282 an, 282 bncan be integrally provided for the thin plate sections 16 a, 16 b formedas a result of etching or cutting a plate member.

The embodiment described above is illustrative of the case in which theadhesive 200, 202 is formed by means of the screen printing.Alternatively, it is possible to use, for example, dipping, dispenser,and transfer.

Next, explanation will be made with reference to FIGS. 47 to 52 forvarious illustrative constructions concerning the adhesive 202 whichintervenes, for example, between the thin plate section 16 a and thestacked type piezoelectric/electrostrictive element 24 and the adhesive200 which intervenes between the thin plate sections 16 a, 16 b, themovable section 20, and the fixation section 22.

At first, in the first technique shown in FIG. 47, a large number ofholes 290 are provided through the thin plate section 16 a. The stackedtype piezoelectric/electrostrictive element 24 is glued to a portion atwhich the holes 290 are provided, by the aid of the adhesive 202. Inthis arrangement, the adhesive 202 enters the inside of the boles 290.Therefore, the adhesion area is substantially increased, and it ispossible to use a thinner adhesive 202. It is preferable that thethickness of the adhesive 202 is not more than 5% of the total thicknessof the stacked type piezoelectric/electrostrictive element 24 and notless than a thickness of such a degree that the thermal stress due tothe difference in coefficient of thermal expansion between the thinplate section 16 a and the adhesive 202 can be absorbed.

It is preferable that the diameter of the hole 290 is 5 μm to 100 μm.The arrangement pattern may be either a matrix form or a zigzagarrangement. Of course, a plurality of holes 290 may be arranged in onearray. It is preferable that the arrangement pitch of the holes 290 is10 μm to 200 μm. Alternatively, recesses (bores) may be used in place ofthe holes 290. In this arrangement, it is preferable that the diameterof the bore is 5 μm to 100 μm. The arrangement pattern may be either amatrix form or a zigzag arrangement. It is preferable that thearrangement pitch of the bores is 10 μm to 200 μm. Especially, in thecase of the recess (bore), for example, it is also preferable to use arectangular configuration as viewed in plan view with its opening areawhich is slightly smaller than the projection area of thepiezoelectric/electrostrictive element 24 onto the thin plate section 16a. Those adoptable as the technique for forming the holes 290 or thebores in the thin plate section 16 a include, for example, etching,laser machining, stamping, drill machining, electric dischargemachining, and ultrasonic machining.

In the second technique shown in FIG. 48, the surface 292 of a portionof the thin plate section 16 a, on which a stacked typepiezoelectric/electrostrictive element 24 is formed, is roughened bymeans of the blast treatment, the etching treatment, or the platingtreatment. In this arrangement, the lower surface 294 of the stackedtype piezoelectric/electrostrictive element 24 is also roughened.Accordingly, the adhesion area is substantially increased. Therefore, itis possible to use a thin thickness of the adhesive 202.

FIG. 48 is illustrative of the case in which the surface of the thinplate section 16 a and the lower surface of thepiezoelectric/electrostrictive element 24 (surface opposed to the thinplate section 16 a) are roughened. However, it is enough that thesurface having the small adhesion force with respect to the adhesive 202is roughened. A sufficient effect is obtained, for example, even whenonly the surface of the thin plate section 16 a is roughened. Thesurface roughness is preferably Ra=0.1 μm to 5 μm, and more preferably0.3 μm to 2 μm, for example, as estimated by the center line averageroughness.

In the third technique shown in FIG. 49, a curvature 296 is provided forthe stick-out shape of the adhesive 200, especially for the stick-outshape of the adhesive 200 toward the hole (hole 252 of the substrate258) formed by the inner walls of the thin plate sections 16 a, 16 b,the inner wall 20 a of the movable section 20, and the inner wall 22 aof the fixation section 22. In this arrangement, it is preferable thatthe radius of curvature is not less than 0.05 mm and up to the extentthat the stick-out shape is linear, or the stick-out shape includes alinear portion. The formation of the curvature 296 for the stick-outportion of the adhesive 200 can be realized, for example, by inserting acylindrical core member into the hole 252 before curing the adhesive200. Practically, the control is made based on the use of theapplication amount and the physical property of the adhesive 200 so thatthe stick-out shape is at least not convex.

Accordingly, the inner wall 20 a of the movable section 20, the innerwall 22 a of the fixation section 22, and the inner walls of therespective thin plate sections 16 a, 16 b are also used as the adhesionsurfaces. Therefore, the adhesion area is increased, and it is possibleto increase the adhesion strength. Further, it is possible toeffectively disperse the concentration of the stress on the joinedportions (angular portions) between the inner wall 22 a of the fixationsection 22 and the inner walls of the respective thin plate sections 16a, 16 b.

In the fourth technique shown in FIG. 50, angular portions opposed tothe fixation section 22, of angular portions of the movable section 20,and/or angular portions opposed to the movable section 20, of angularportions of the fixation section 22 are chamfered respectively to formtapered surfaces 298. The stick-out amount of the adhesive 200 can bestabilized by appropriately adjusting the radius of curvature and theangle of the chamfering. It is possible to suppress the local dispersionof the adhesion strength, and it is possible to improve the yield.

The following method is preferably used to chamfer the angular portion.That is, for example, the cutting and the polishing are performedbeforehand for the portions to be formed into the angular portions ofthe first support section 264 and the second support section 256 to formthe tapered-surfaces 298 before the assembling. Of course, thechamfering may be performed after the assembling. In this case, forexample, the laser machining, the ultrasonic machining, or the sandblastis preferably adopted.

The fifth technique shown in FIG. 51 relates to the punching out processwhich is usually performed, for example, when the thin plate sections 16a, 16 b are manufactured. In this case, burrs 300 are formed. The formedburrs 300 may be removed before the assembling. However, they may beallowed to remain as they are. In this case, it is preferable that thedirections of the formed burrs 300 are regulated, for example, inconsideration of the handling and the adhesion directions of therespective members as well as the easiness of control of the amount ofthe adhesive. The example shown in FIG. 51 is illustrative of a state inwhich the burrs 300 of the thin plate sections 16 a, 16 b are directedoutwardly.

In the sixth technique shown in FIG. 52, the thickness of the first thinplate section 16 a is made to be larger than the thickness of the secondthin plate section 16 b as described above. In the case of the use asthe actuator section 204 and the sensor, the stacked typepiezoelectric/electrostrictive element 24 is preferably formed on thefirst thin plate section 16 a.

Other techniques are also available. For example, when the stacked typepiezoelectric/electrostrictive element 24 is glued to the thin platesection 16 a, 16 b by the aid of the adhesive 202, for example, it ispreferable that a ZrO₂ layer is allowed to intervene as an underlyinglayer for the lower surface of the stacked typepiezoelectric/electrostrictive element 24.

When the stainless steel thin plates 260, 262 (for example, see FIG. 33)are used as the thin plate sections 16 a, 16 b, it is preferable thatthe longitudinal direction of the thin plate sections 16 a, 16 b isapproximately coincident with the direction of the cold rolling appliedto the stainless steel thin plates 260, 262.

It is preferable that the piezoelectric/electrostrictive layer 26 forconstructing the stacked type piezoelectric/electrostrictive element 24is stacked in about three layers to ten layers.

The piezoelectric/electrostrictive devices 10A, 10B described above canbe utilized as the active device including, for example, varioustransducers, various actuators, frequency region functional parts(filters), transformers, vibrators, resonators, oscillators, anddiscriminators for the communication and the power generation, as wellas the sensor element for various sensors including, for example,ultrasonic sensors, acceleration sensors, angular velocity sensors,shock sensors, and mass sensors. Especially, thepiezoelectric/electrostrictive devices 10A, 10B described above can bepreferably utilized for various actuators to be used for the mechanismfor adjusting the displacement and the positioning and for adjusting theangle for various precision parts such as those of optical instrumentsand precision mechanical equipments.

It is a matter of course that the piezoelectric/electrostrictive deviceand the method for producing the same according to the present inventionare not limited to the embodiments described above, which may beembodied in other various forms without deviating from the gist oressential characteristics of the present invention.

1. A method for producing a piezoelectric/electrostrictive devicecomprising: a pair of mutually opposing thin plate sections, and afixation section for supporting said thin plate sections; and one ormore piezoelectric/electrostrictive elements arranged on at least onethin plate section of said pair of thin plate sections, said methodcomprising the steps of: preparing a plurality of thin plates, saidpiezoelectric/electrostrictive element, and a support substrate;securing said piezoelectric/electrostrictive element to at least one ofsaid thin plates by the aid of a first adhesive; securing said pluralityof thin plates to said support substrate by the aid of a second adhesiveto manufacture a master device block including said plurality of thinplates disposed opposingly; and dividing said master device block into aplurality of chips to manufacture each saidpiezoelectric/electrostrictive device, wherein at least portions of saidplurality of thin plates define said thin plate sections.
 2. The methodfor producing said piezoelectric/electrostrictive device according toclaim 1, wherein: said pair of thin plate sections of saidpiezoelectric/electrostrictive device include open ends for holding anobject member; and said support substrate is a rectangular annularstructure having a portion defining said object member, and a portiondefining said fixation section.
 3. The method for producing saidpiezoelectric/electrostrictive device according to claim 1, wherein:said pair of thin plate sections of said piezoelectric/electrostrictivedevice include open ends; and said support substrate is a rectangularannular structure having a portion for supporting said open ends, and aportion defining said fixation section.
 4. The method for producing saidpiezoelectric/electrostrictive device according to claim 1, wherein atleast one of said first adhesive and said second adhesive comprisesorganic resin.
 5. The method for producing saidpiezoelectric/electrostrictive device according to claim 1, wherein atleast one of said first adhesive and said second adhesive comprises oneof glass, brazing material, and solder.
 6. The method for producing saidpiezoelectric/electrostrictive device according to claim 1, wherein atleast one of said thin plates and said support substrate comprisesmetal.
 7. The method for producing said piezoelectric/electrostrictivedevice according to claim 1, wherein: said step of dividing said masterdevice block further comprises a treatment for cutting said masterdevice block along predetermined cutting lines; and said cutting isperformed in substantially the same direction as a displacementdirection of said pair of thin plate sections.
 8. The method forproducing said piezoelectric/electrostrictive device according to claim1, further comprising the step of forming an underlying layer on asurface of said piezoelectric/electrostrictive element opposed to saidthin plate before securing said piezoelectric/electrostrictive elementto said thin plate by the aid of said first adhesive.
 9. The method forproducing said piezoelectric/electrostrictive device according to claim1, further comprising the step of forming one or more holes or recessesat least at a portion of said thin plate to which saidpiezoelectric/electrostrictive element is secured.
 10. The method forproducing said piezoelectric/electrostrictive device according to claim1, further comprising the step of roughening at least a portion of asurface of said thin plate to which said piezoelectric/electrostrictiveelement is secured.
 11. The method for producing saidpiezoelectric/electrostrictive device according to claim 1, furthercomprising the step of forming a curvature for a stick-out shape of saidsecond adhesive protruding from an opposing portion between said thinplate and said support substrate.
 12. The method for producing saidpiezoelectric/electrostrictive device according to claim 1, furthercomprising the step of chamfering mutually opposing angular portions ofsaid support substrate of said master device block.
 13. The method forproducing said piezoelectric/electrostrictive device according to claim1, further comprising the step of: manufacturing said thin plate bystamping a metal plate, wherein: when said master device block isproduced by combining said thin plate with said support substrate, aburr, which is brought about on said thin plate due to said stamping, isdirected outwardly to produce said master device block.
 14. A method forproducing a piezoelectric/electrostrictive device comprising: a pair ofmutually opposing thin plate sections, and a fixation section forsupporting said thin plate sections; and one or morepiezoelectric/electrostrictive elements arranged on at least one thinplate section of said pair of thin plate sections, said methodcomprising the steps of: preparing a plurality of thin plates, saidpiezoelectric/electrostrictive element, and a support substrate;securing said plurality of thin plates to said support substrate by theaid of a second adhesive; securing said piezoelectric/electrostrictiveelement to at least one of said thin plates by the aid of a firstadhesive to manufacture a master device block including said pluralityof thin plates disposed opposingly; and dividing said master deviceblock into a plurality of chips to manufacture each saidpiezoelectric/electrostrictive device, wherein at least portions of saidplurality of thin plates define said thin plate sections.
 15. The methodfor producing said piezoelectric/electrostrictive device according toclaim 14, wherein: said pair of thin plate sections of saidpiezoelectric/electrostrictive device include open ends for holding anobject member; said support substrate is a rectangular annular structurehaving a portion defining said object member, and a portion definingsaid fixation section.
 16. The method for producing saidpiezoelectric/electrostrictive device according to claim 14, wherein:said pair of thin plate sections of said piezoelectric/electrostrictivedevice include open ends; and said support substrate is a rectangularannular structure having a portion for supporting said open ends, and aportion defining said fixation section.
 17. The method for producingsaid piezoelectric/electrostrictive device according to claim 14,wherein at least one of said first adhesive and said second adhesivecomprises organic resin.
 18. The method for producing saidpiezoelectric/electrostrictive device according to claim 14, wherein atleast one of said first adhesive and said second adhesive comprises oneof glass, brazing material, and solder.
 19. The method for producingsaid piezoelectric/electrostrictive device according to claim 14,wherein at least one of said thin plates and said support substratecomprises metal.
 20. The method for producing saidpiezoelectric/electrostrictive device according to claim 14, wherein:said step of dividing said master device block further comprises atreatment for cutting said master device block along predeterminedcutting lines; and said cutting is performed in substantially the samedirection as a displacement direction of said pair of thin platesections.
 21. The method for producing saidpiezoelectric/electrostrictive device according to claim 14, furthercomprising the step of forming an underlying layer on a surface of saidpiezoelectric/electrostrictive element opposed to said thin plate beforesecuring said piezoelectric/electrostrictive element to said thin plateby the aid of said first adhesive.
 22. The method for producing saidpiezoelectric/electrostrictive device according to claim 14, furthercomprising the step of forming one or more holes or recesses at least ata portion of said thin plate to which saidpiezoelectric/electrostrictive element is secured.
 23. The method forproducing said piezoelectric/electrostrictive device according to claim14, further comprising the step of roughening at least a portion of asurface of said thin plate to which said piezoelectric/electrostrictiveelement is secured.
 24. The method for producing saidpiezoelectric/electrostrictive device according to claim 14, furthercomprising the step of forming a curvature for a stick-out shape of saidsecond adhesive protruding from an opposing portion between said thinplate and said support substrate.
 25. The method for producing saidpiezoelectric/electrostrictive device according to claim 14, furthercomprising the step of chamfering mutually opposing angular portions ofsaid support substrate of said master device block.
 26. The method forproducing said piezoelectric/electrostrictive device according to claim14, further comprising the step of: manufacturing said thin plate bystamping a metal plate, wherein: when said master device block isproduced by combining said thin plate with said support substrate, aburr, which is brought about on said thin plate due to said stamping, isdirected outwardly to produce said master device block.
 27. A method forproducing a piezoelectric/electrostrictive device comprising: a pair ofmutually opposing thin plate sections, and a fixation section forsupporting said thin plate sections; and one or morepiezoelectric/electrostrictive elements arranged on at least one thinplate section of said pair of thin plate sections, said methodcomprising the steps of: preparing a plurality of thin plates, saidpiezoelectric/electrostrictive element, and a support substrate;securing said plurality of thin plates to said support substrate bydiffusion joining or welding, said thin plates being disposedopposingly; securing said piezoelectric/electrostrictive element to atleast one of said thin plates by the aid of a first adhesive tomanufacture a master device block; and dividing said master device blockinto a plurality of chips to manufacture each saidpiezoelectric/electrostrictive device, wherein at least portions of saidplurality of thin plates define said thin plate sections.
 28. The methodfor producing said piezoelectric/electrostrictive device according toclaim 27, wherein: said pair of thin plate sections of saidpiezoelectric/electrostrictive device include open ends for holding anobject member; and said support substrate is a rectangular annularstructure having a portion defining said object member, and a portiondefining said fixation section.
 29. The method for producing saidpiezoelectric/electrostrictive device according to claim 27, wherein:said pair of thin plate sections of said piezoelectric/electrostrictivedevice include open ends; and said support substrate is a rectangularannular structure having a portion for supporting said open ends, and aportion defining said fixation section.
 30. The method for producingsaid piezoelectric/electrostrictive device according to claim 27,wherein said first adhesive comprises organic resin.
 31. The method forproducing said piezoelectric/electrostrictive device according to claim27, wherein said first adhesive comprises glass, brazing material, andsolder.
 32. The method for producing said piezoelectric/electrostrictivedevice according to claim 27, wherein at least one of said thin platesand said support substrate comprises metal.
 33. The method for producingsaid piezoelectric/electrostrictive device according to claim 27,wherein: said step of dividing said master device block furthercomprises a treatment for cutting said master device block alongpredetermined cutting lines; and said cutting is performed insubstantially the same direction as a displacement direction of saidpair of thin plate sections.
 34. The method for producing saidpiezoelectric/electrostrictive device according to claim 27, furthercomprising the step of forming an underlying layer on a surface of saidpiezoelectric/electrostrictive element opposed to said thin plate beforesecuring said piezoelectric/electrostrictive element to said thin plateby the aid of said first adhesive.
 35. The method for producing saidpiezoelectric/electrostrictive device according to claim 27, furthercomprising the step of forming one or more holes or recesses at least ata portion of said thin plate to which saidpiezoelectric/electrostrictive element is secured.
 36. The method forproducing said piezoelectric/electrostrictive device according to claim27, further comprising the step of roughening at least a portion of asurface of said thin plate to which said piezoelectric/electrostrictiveelement is secured.
 37. The method for producing saidpiezoelectric/electrostrictive device according to claim 27, furthercomprising the step of chamfering mutually opposing angular portions ofsaid support substrate of said master device block.
 38. The method forproducing said piezoelectric/electrostrictive device according to claim27, further comprising the step of: manufacturing said thin plate bystamping a metal plate, wherein: when said master device block isproduced by combining said thin plate with said support substrate, aburr, which is brought about on said thin plate due to said stamping, isdirected outwardly to produce said master device block.